A subframe question (just the beginning ...)
 

Today I bit the bullet and ordered all the rear subframe linkage for my 87 300D, which is pretty much just decrepit back there at this point. Other than the swaybar, sway links and shocks, everything is original, and it's time for the next round. I'm also planning on swapping out the subframe itself for one I got from an 88 300E ... mine has a crack under the diff (which can probably be welded, but I have this nice frame in my shed so might as well use it).
The only thing I didn't order was springs ... they don't look bad and I'm not sure how to assess whether they ought to be replaced, too. One thing I can tell you is my car lilts to the right in the rear ... perceivably. Is that likely because of the worn linkage, or should I consider it a sign the springs are in need of replacement as well? To be honest, I'm not entirely sure the physics or what holds what up, beyond the basics.
I don't want to finish the job and have it still lilt because I left worn springs in there, but I also don't want to throw out perfectly good springs. Thoughts would be appreciated.
I won't start this project for a couple weeks at least, so take your time. I also might wimp out and take it to my indy ... ;)

some one should be able to tell you the free length of the springs, as you look like you are going to have a complete disassemble/rebuild you will be able to check the lenght.

Spring replacement is relatatively minor:D compared to the rest of the job. I'd do all else then see if the listing to the side is still there. Also, spring compressor is not absolutely required, but does make it easy.

I agree with Hanno, dropping the subframe is a big, big job. By comparison spring replacement is about 2% of the total job - I'd keep your springs and see how things look. It's certainly possible a collapsed subframe bushing could cause the car to sag on one side a little bit.

One thing you want to check before you go too far with this plan is the bolts that hold the subframe to the unibody. They are usually very tight and 25 years of living in a fairly corrosive environment doesn't help. If you snap one of these bolts off you are going to have a much bigger job on your hands.

Here are some pictures from Dave's website that show various stages of the process.

http://www.w124performance.com/images/W124_subframe/

Dave's website is a godsend!:D Yes, my bolts do look pretty corroded. Are there steps I can take to make sure I don't snap one (aside from the obvious PB Blaster soaking)? Or is this a case of assuming it's going to snap no matter what. If it's a strong likelihood, I guess I may reconsider ... that could turn into disaster fast.

to prevent bolt breakage, after you have the car secured on stands, hit all bolts with a BFH I mean wail on them serious, then soak them down with aerokroil or PB blaster. try to get the spray on the bolt threads from inside the framerails if you can.

PB blaster is no comparison to AeroKroil. The runner-up is Liquid Wrench Penetrant. I use it with excellent results.

Ah AeroKroil ... I knew there was one on the market that had a really god rep but couldn't remember that name. Thanks. I'll order some.

The only part you can see from underneath is the bolt head, so that is not much of an indicator. The subframe bolts are very fine thread which screw into internally threaded tubes extending downward from the chassis. Spray penetrants may help somewhat with any corrosion between the bolt head and the washer/plate above it but not much more I’d suspect.

The subframe bolts use blue threadlock so as with any blue threadlocked fastener a very useful tactic is to use a propane torch to heat the fastener for a minute or two perhaps. The fastener doesn’t need much heat, blue threadlock softens at about 150 F so if you get the head of the bolt a little too hot to touch with your finger that’s about right. In the case of the subframe bolts heating the head will by convection heat the treaded shaft so you shouldn’t have any problem.

I have done complete subframe rehabs on 4 or 5 of my personal 124 cars and on a pair of my 201 cars and have never had a problem with a subframe mount bolt, I’ve done another dozen or so on other cars and the only problem was one car that had been hit in the rear, the subframe tweaked and as a result the bolt and its receptacle where bent some which put some lateral friction on the bolt as it was being removed.

The bolts and nuts securing the various multi links will deserve some attention where a penetrant like Kroil is well worth the $15 a can costs.

With regard to the rear springs, try to get a look at the ends of the springs, there is a tendency for the first coil or a portion of it to break off with age and mileage. It’s kind of hard to see it because it’s down inside the rear LCA.

I haven’t priced springs of late but they used to be about $100 for the pair, it would seem a relatively small additional investment to have a new rear suspension! New rubber spacers would be in order also but you’ll really need to get everything installed and rode in before you can determine the actual ride height and what thickness spacer will be appropriate.

Bodhi,
The ASME did tests s few years ago on various anti seize products. The best result by far was a 50/50 mix of acetone (nail polish remover) & atf. I guess you have both of these!! :D
Give it a try, it works for me. I get into trouble for "borrowing" nail polish remover, but what the heck!!

Lots of great info from Billlybob, my success rate on subframe bolts is more like 50/50 but I have to admit that on all the cars I've had problems with they were shall we say??...... I bit crusty underneath to begin with so maybe I'm a bit more pessimistic than I should be.

The heat trick sounds like a good play but I'm always a little leery of using heat in the immediate vicinity of rubber (like subframe bushings) once that kind of rubber starts to burn it can be non-trivial to put out the fire, and boy does it generate a lot of black acrid smoke!!! Maybe heating the whole assembly with an electric heat gun would be a good way to go?

One other thing worth noting in Dave's pictures is that he jacked up the rear of the car but left the front wheels on the ground - even if you have access to a lift I'd recommend this approach because sometimes if a car is on a lift and you remove a very heavy component (like a subframe) it can actually upset the balance to the point where the car can become unstable on the lift. With the front wheels on the ground (and properly secured) this would not be an issue.

X2 Jim on keeping front wheels on the ground. Many of these jack stands are not very stable. I use a couple of pieces of 18" diameter tree trunk. You can push as hard as you like on the car & they wont topple over. I have used a couple of wheels stacked on each other as a safety measure on the side of the road.
Bodhi,
Before you get under it, give it a good solid side ways shake to make sure its not going to move !! if you can make it wobble on the jack stands, its no good!!

OK guys, I'm back from London, past jetlag, and ready to dig in on this. I got the "new" subframe from my parents' shed and have removed most of the linkage from it (one arm won't come off because the bolt is rusted to the inside of the bushing:mad:). I also picked up my great big box of new parts from the dealer and ordered two cans of Kroil and pint of POR15 black. And I printed out most of the FSM pages regarding this job. Couple questions remain:
-Tools. Which ones do I need and where do I find them? I can't find any diff mount tools on eBay and I know I need that one. Do I need to use the subframe mount tool when removing installing the bushings with the frame off the car, or is there another legit way? Also, do I need a special pusher to remove the axle shaft from the wheel carrier? Do I even have to remove it from the wheel carrier, or can I remove it at the diff and just pull the carrier and axle off together to be reinstalled on the new frame? Any other tools I'll need that I haven't considered yet?
-The FSM says to remove the spring link, just unbolt it from the wheel carrier ... do I have to worry about the spring popping out when I unbolt the shock? I understand a spring compressor is not needed for the rears, but I have an underlying fear of spring beheadings.
-The FSM says to torque all linkage with the axle horizontal. I take this to mean with the wheels on the ground or supported. Am I correct?

Thanks. I'm off to organize my big box o' parts and unload the subframe out of my Jeep.:D

pm sent about compressor availability.

Fasteners for the links get tightened with wheels on ground or supported so that weight of car is loading the suspension in driving position.

The amount of force needed to free the subframe bolts could be enough to topple the jackstands, so as stated above I'd have the front wheels on the ground. Additional belt and suspenders approach is to use a long pipe as your breaker bar extender. You can really pull on it when it extends out from under the car (puts you out from under also:D).

Can't help with the diff mounts, never did them.

As you’re working on the subframe out from under the vehicle everything will be easier.

Diff mounts – first thing is to measure the distance from the rearmost part of the tapered opening for the mounts in the subframe to the rear edge of the mount’s outer steel tube. This dimension is what you want to replicate when your new mounts are eventually installed. The diff mounts can be R&R’d with the correct tool or with a large socket/bolt/washer facsimile if you don’t have a large socket a steel Female-Female pipe coupling for either black steel pipe or EMT can be had at most hardware stores or the Home Depot type’s for a couple dollars. With a coupling you’ll need some type of plate with a hole large enough for the bolt, if you make use of a large socket you’ll just need a thick washer or two after threading the bolt through the ½” drive hole. You can use this ad hoc tool to install the new mounts and by reversing it to remove the old ones.

A similar tool can be assembled from a large 4” dia. pipe coupling some steel plate or a pipe end cap with a hole for the bolt drilled in its center as a puller for the sub frame mounts.

The subframe mounts can be very difficult to get out without some type of puller, but if you're going to be repainting the subframe anyway prying them or even using a torch to burn the rubber free is an option. Of course you’ll need to clean that area afterwards and repaint it to prevent rust. When installing the subframe mounts, set up your ad hoc screw type puller and squeeze them into place. That install is made easier if you coat the mount and the cup into which it will install with a liberal slathering of personal lubricant, i.e. KY or its generic equivalent. You don’t want to use a petroleum product for two reasons it will degrade the mount’s outside rubber surface and it will remain slippery, the remaining slippery thing is the same reason you don’t use rubber friendly lubes like silicon based lube. The personal lube is slippery as heck when it’s wet but after it dries it isn’t because it’s really gelatin based and it won’t impact the rubber material.

The axles will come free of the wheel carrier using a brass drift, usually quite easily. The axle nut is a 30 mm 12 point, the interface section is rather shallow, so a good socket is best but a cheaper socket can have it’s initial 1/8” radius ground off to allow a better fit on the nut. A small cold chisel can bend or break the crimped collar out of the securing cut in the axle’s end. The nut comes from the factory treated with micro-encapsulated blue thread lock, with the collar unbent set up a counter brace using a couple lug bolts and a piece of pipe on the wheel hub, then heat the nut and when it’s too hot for your finger put the socket/breaker bar to it. It’s usually a little hard to crack it free but it comes off easily once it does. If you’ve got a decent impact gun and a good socket you can often blast that nut off without even worrying about the crimped collar!

You’ll want the axles off and out of the wheel carriers just because they will be ungainly when trying to move things that last mm to get a bolt to slide into place!

When you get to the point of removing what is on the car now. This is the way I do it. Jack and support the car, disconnect the rear flex disk and swing the driveshaft over a bit and hang it with a wire or bungee cord, disconnect the ABS sensor inside the car behind the rear seat, the screw holding the clip holding the wire and push the connector and the rubber grommet out through the hole in the chassis, pull the wheels of and then remove and hang the rear calipers, unfasten the rear sway bar either at its end or the wheel carrier (alternatively you can unfasten the rear sway bar from it’s mounts to the chassis, these are usually rusted and a little hard to get to so I just disconnect and remove it after the subframe is out of the way), then using your breaker bar and a 19 mm 6-point socket break the sub frame mount bolts loose, on the passenger side there is the fuel fill overflow/drain hose that threads down through holes in the subframe, work that free if you can or at least loose so it can come free. Then put the wheels back on with a couple lug bolts, I lower the car down to the ground, unfasten the shocks at the top, and remove the four subframe bolts. Then you can use a pair of jacks to lift the car up off the sub frame nice and slow and controlled! Once the rear of the car is high enough the springs will be free, and you will be able to roll the entire sub frame out from under the elevated rear of the car on its two wheels!

If you are thoughtful and methodical you can carefully chock the front wheels and use a pair of Mercedes standard screw type jacks to lift and lower the rear of the vehicle going from side to side raising each a couple inches each time, of course that depends on good jack holes! For controlled lifting and lowering a screw type jack offers more control than hydraulic jacks particularly when lowering when you’re doing stuff like this. Over time I’ve accumulated an assortment of pairs of GM bottle type screw jacks, scissor type screw jacks, hydraulic bottle jacks, and other weird configurations just to have for jobs like this.

P. S. when doing stuff like I have a pile of 4" X 4" and 6" X 6" sections of landscape type timbers 1-2' long and a couple 3-4' long. When I'm doing something where I might be applying serious force to big fasteners where you could shift the car, instead of jack stands with a small surface area contact to the underside of the car, I use these timbers to in a criss-cross fashion in the manner that is used for cribbing under boats in dry dock. It's like building a temporary platform under the vehicle. Once you jack the car up, set the cribbing and lower the car onto it, there's no way to shake the car off it.

I almost forgot you will also need to unbolt the exhaust, it's easiest to do that at the joint between the down pipe section and the resonator, then either free the exhaust from the hanger at the subframe or unbolt that mount from the subframe, and lift the muffler off the hangers at the rear. Then you can just slide that part of the exhaust out from under the car. The joint between the muffler and resonator is a slip joint and usually is quite difficult to seperate particularly when you're under the car! The rubber exhaust mount at the subframe will likely be stretched and cracking, replacing it will never be easier and if you do your exhaust will not hang as low.

Billybob, thanks so much for that writeup ... it's really a huge help, more helpful than the FSM so far!:D
Unfortunately I'm stuck on getting the subframe mounts out of the replacement subframe. I've tried making a tool out of a harbor freight bearing puller bracket mounted on a long bolt and large washers and a nut, but the bracket is not strong enough, plus I can't find a washer that will push on the bottom of the mount evenly (it just kind of squishes it down) ... I'll try the pipe and plate method if I can find anything at Home Depot. I just wish the puller tool was available for rent in the tool rental list. I'm going to spend the next week just trying to make a tool and I'm really not good at that sort of thing, even though I have the basic idea in my mind. Frustrating.:(

Damn! Sorry, I usually tend to shy away from directly promoting the rental of my tools in threads I respond to, a little too self-serving. I figure if someone is looking for a tool to rent they will find it in the Tool Rental Thread, but I haven't listed the Klann tool for removing the rear sub-frame bushing mounts on 124/129/201 vehicles which I have available!

The proper tool, although it is designed to be used with the sub-frame still on the vehicle and it does a great job doing so, can of course be used directly on the mounts with the subframe off the vehicle also.

The mounts can be extremely difficult to remove as the outer rubber almost fuses to the sub-frame and every time you attempt to pull it the rubber just stretches. As I mentioned in the past I've applied fire to the area of the subframe into which the mount installs, once the area is hot enough, usually rubber in flames! The burning mount can be more easily removed (but flaming, melting, napalm-like rubber drops not withstanding)! Then after the destruction you can clean and repaint that area.

If you decide the correct tool is the way you want to proceed PM me and I'll send you the rental particulars, you could have it in about two days.

best cheater in the world is the floor jack handle... simple and easy, and most everyone working on cars has one.

Excellent Post/Replys
 

This whole Post (In Conjunction with GSXR's Photos ) should be a DIY "STICKY".

Just a little update: Thanks to Billybob, Timfreeh and hanno, I have been able to make some strides using the factory tools. Everything is off the replacement subframe, and I spent over an hour yesterday sanding, degreasing and scrubbing clean the frame. Tomorrow I'll touch up with black POR15. For the most part the frame looks good.
http://sphotos.ak.fbcdn.net/hphotos-..._2034903_n.jpg
I did have to sawzall off one arm where the bolt had frozen to the bushing. And the front subframe mounts, even with the official tool, were a bear (but boy did that tool make the rear ones easy!!) ... one of them exploded and shot black oil in every direction. I had wondered if the mounts had a fluid in them like the motor mounts, but wouldn't have expected a thin black oil.:confused:
http://sphotos.ak.fbcdn.net/hphotos-..._3728194_n.jpg
Anyhow, after the center of each bushing was out via the tool, I used a punch, screwdriver and pry bar (plus torch) to carefully pry out the shell of the bushing. The large bushings came out great.
So, after the paint dries I'll put all the new bits on the frame. Of course the intimidating part is actually dropping and replacing the frame on the car. I'm debating putting that part off until the end of the month. I have a trip to Virginia (four-hour drive) I'd like to make on Oct. 26 and 27, and I know if I drop the frame I'll likely have several delays and won't have the car for then. On the other hand, I hesitate to drive it so far with the diff mounts in such poor condition. It drives great, other than drifting a bit at 70-80 mph. But still, kind of worries me. I'd like to work up the guts to drop it this weekend, but knowing how things go with me, something will get stuck, broken, lost ... and the car will be up on jackstands for three weeks.:P
One step at a time ... I'll post an update when I get the replacement frame done.:o

New question!
I was giving the FSM a thorough read last night and noticed for re-installation of the bolts holding the subframe to the floor it says "re-cut thread on frame floor." I haven't heard this mentioned elsewhere. Is it necessary and what exactly does it entail?
Also, should I replace the three flex disc nuts I remove? I just did the driveshaft in April but I know they're self-locking so maybe I should get new ones.

Edit to add more Qs:
-Each bolt kit comes with three bolts, one hex head and two 12pt allen heads. Sorry to be thick, but which am I supposed to use? There are only two places to put bolts on each arm as far as I know.
-The arms come without the centering sleeves installed, but I have them separate. The FSM shows them already installed, so I'm not sure how to put them on the end of the arm. Do I just tap them in or is there any science to it?
-How far should I press the differential bushings in? I was very careful with the clocking, but not sure how far to go in ... the FSM uses the pressing in tool as a reference but the tool I am using is slightly different. On my subframe and the spare subframe, the mounts were at completely different depths, so I can't really use that as a reference because one of them must have been wrong.
-If I can get a good purchase on the bolt, is there any reason I can't break loose the rear subframe bolts with the car on the ground? Then tighten them by hand, raise car and proceed. The front bolts look decent. The rear ones look like a nightmare waiting to happen. Does having the weight off the frame help break them loose? Because I think I may have enough leverage with it on the ground.

Thanks.:o Overwhelmed by this right now; it's just making me feel stupid.

A little progress ... I finally stopped staring at stuff and actually dug in. I got ALL four subframe bolts to turn! The rear ones really worried me because they are very corroded and a bit deformed. I Kroiled them, then used a pointy punch to scrape the base of each side so the socket would fit all the way on. Because I was so afraid the socket would slip and strip the bolt, I placed a scissor jack underneath the head of the breaker bar to keep pressure on the bit while I stood back with a pipe extension and pushed. It worked! Attached a pic.
Now I'm going to remove the wheel carriers (or try) and all the bits and pieces before lowering the frame.
I'm having some trouble the with exhaust, specifically the hardware holding the assembly on at the middle (four bolts/nuts). The nuts won't turn for anything and are sort of stripping. They look like they have a little collar on the outside of them. Any trick to this or are they just seized on? I sprayed Kroil and will try again in a bit.
ALSO, do you think it would be OK to remove the axle nut with an impact wrench? I don't know if I'll have much luck getting that off ... that's a lot of torque, man. I'm almost afraid to try.

Ugh ... when I push really hard on the axle nut, it overcomes the parking brake. Is that a sign I need to tighten my parking brake? I haven't taken the calipers off yet so should I just use a board or pipe to hold down the actual brakes?

The 30 mm 12 point nut? I assume that you don't have a 1/2" drive impact gun? The parking brake will never hold it! If so you will need to use a couple wheel bolts screwed into the hub and a piece of pipe or something similar to brace the hub from turning. Break out or bend out the collar of the nut from the cut on the axle stub, to allow it to turn easier. Then you can use a large breaker bar possibly a pipe extension on that! In my experience the best thing to do is to heat the nut too hot to touch with a propane torch and then while it is still hot put the tool to it, keep the tool straight and square to the nut and put your weight to it.

The working surface of the nut is pretty thin so if you have a socket with significant radius at its opening you can grind off that radius to allow more of the tool working surface to make more and better contact with the nut's surfaces.

Read and answered your latest post first! Good job on the sub frame mount bolts. Getting them out without problems is an important accomplishment!

The exhaust bolts should be considered sacrificial, just break out the angle grinder with a thin blade and be done with them! Or just break them by over-torquing them but sometimes you just bust the nut or the head off and you've got to hammer things apart then anyway, cutting the bolts between the flanges gets things apart and you can deal with the nuts and bolt stubs separately. When you put things back together slather the new bolts and nuts with Permatex Never-Seize!

I would very much recommend just disconnecting the just the rear sway bar, the driveshaft and hanging the calipers and then dropping the entire sub frame assembly as a unit. You will be able to get to all the link ends bushings etc. so much easier with it on the ground and out from under the car, especially if something gives you a problem. Get that stuff disconnected, get your jack under the differential and raise it a touch then remove the sub frame mount bolts. When you remove the front ones the entire sub frame tends to want to swing downwards, I just place a scissors jack under the front of the differential and crank that up to support it evenly in place. That way after the front bolts are removed the subframe is not hanging and causing the rear mounts to be twisted forwards and harder to drop free. Just remember to disconnect the ABS sensor before dropping things, they break and they’re expensive!

The only concern I had with dropping the whole thing is the added weight ... the sub and diff by itself don't scare me nearly as much as the whole thing with the wheel carriers. Although I guess I would not have to be underneath it. I liked the idea you posted earlier of putting the car back on the ground and lifting it off the frame, but I don't have a way of jacking up the car evenly and getting jackstands under it.
If I do drop the whole thing (which is starting to appeal to me), should I still break loose the axle nut while it's on the car? I'm thinking it would be really hard to do when it's on the loose frame on the floor. The pipe and lugnut idea sounds like it will work, plus torching. I do have an impact wrench my dad is going to lend me, and an air compressor ... but I'll try heating it and using the breaker bar and pipe again first.
I'll pick up the exhaust bolts at the dealer tomorrow, plus I'm going to order carrier bearers ... for some reason I thought those were OK, but one looks really bad on closer inspection, better change 'em now while I'm digging in.
Thanks!!!

ugh! I hope you REALLY like all that snow and cold up in mile high area! you should go over with us what you are doing to the replacement subframe for rust preventative. pics of the cleaning and treating with por-15, underbody spray if any, etc. (while, I'll never need any of these tips down here in the piedmont of NC, it's nice!)
I don't think a 1/2" impact will get those axle bolts, perhaps a 3/4" or like said, brace the lugs, and use a cheater bar on there!

Cleaning: Hosed off the subframe, brushing off the big clumps of dirt or oil. Then I took my power dremel with a couple different sanding bits and ground off the few areas that had surface rust. Then I used a couple different wire brushes to scrape off remaining rust, crud, oil, etc., and rough up the surface of the whole frame (took a looong time) while continually dousing with POR's Marine Clean and water. I gave it a final scrubbing with the Marine Clean and a scrub brush. Then I painted it with POR 15 black ... very careful to get it in crevasses (but NOT inside the mount cups or diff mount holes ... did not want to alter the way they fit in there!). It looks like a spanking new part:
http://sphotos.ak.fbcdn.net/hphotos-..._1108757_n.jpg
http://sphotos.ak.fbcdn.net/hphotos-..._4486163_n.jpg
As for the underbody of the car ... I will assess when I get the frame down, but I do know I will be doing some work on the protrusions where the front mounts attach. The undercoating is peeling off and I can see rust. I will remove the undercoating, scrap away and use the same POR15 black, plus undercoating on top (not where the mount actually touches). One issue I can see I'm going to have is separating the mounts from the frame ... the metal is rusted to it. Most other areas under the car (including where the rear mounts attach) look clean but I'll inspect more carefully when it's clear under there.
The rocker panels and jack points have to be addressed soon. I'm willing to pay to have someone do it; I just need to find someone. Bodyshops won't touch it because they "don't do restoration" and restoration guys have no interest because it's just an 87 sedan. But that's another story.
I think I'll throw a new muffler on while I've got everything down ... some big holes in the rear and a hole in the pipe going into it ... though I haven't noticed noise/smell/smoke.

Yeah, breaking free the axle nut with everything still on the car will likely be easier than on the ground but not much, the same bolts & bar counter hold method will be needed. I can usually break the axle nuts free with a 1/2" gun without even bending the collar out, but I suppose that depends on the gun and the operating pressure. Try it with the gun first and if that doesn't work you've just got to go old school on it. Now's a good time to make use of the shopping cart you've been saving, cut the basket of and you've got a low to the ground cart! The carts they use under bread racks are perfect and you can get a cheapy moving dolly at home depot and harbor freight also.

The first thing I do is to remove the differential vent and screw a bolt into its place for the time being, that way you can flip the whole subframe over and not have differential fluid leaking out. Then get the lower control arms off that will give you easy access to the six bolts at the axle flange, get them out and pull the axles out of the way, mark what side they came from and you can swap them side to side if you want to. Then I'd do the differential get that out of the way. Then you can more easily flip the sub frame back over and get at everything holding the wheel carrier to the links.

So you want to swap them from side to side? Is that just because they wear differently due to road pitch?

Glad you mentioned the vent on the diff ... I'm sure I would have found a way to spill gear oil everywhere.:o

The design of the CV joints has an outer "chase" an inner "spider" and a number of balls in a holder in between those parts. As the vehicle does most of it's travel in the forward direction the surfaces that make contact under that circumstance get worn the most. By swapping the axles from side to side you then put the lesser worn surfaces which where formerly only in contact when driving in reverse into position of now being in contact when driving forward.

In theory this would lead to longer axle life because you'd end up using both directional surfaces rather than just one. Of course swapping does nothing to aleviate the wear on the balls in the joint but they are pretty tough.

This wear issue is what makes rebuilt axles so undependable, usually the axle core is inspected and measured, if it's in spec they just clean, re-lube, and reboot it. If it's out of spec they regrind the chase and the spider to the next larger size ball, then clean, re-ball, re-lube, and re-boot. The problem is that when the CV joint was originally manufactured the wear surfaces of the chase and the spider are hardened as are the balls, they don't harden the reground surfaces and the axles don't last nearly as long as a result. Now when you combine that functional flaw with Chinese/Mexican/who knows what third world quality control remanufactured axles have become a disposable wear item rather than what was originally a part that might last the life, in the Benz case, long life of the vehicle.

They wear into the other side of the CV joint as they will be rotating the opposite direction.

Thanks guys, that makes sense, but I wouldn't have thought of it! I'll be sure to swap them.:)

I would not swap them side to side.
many many many bearing manufacturers specifically state not to swap wheel bearings from one side to the other due to the bearings wearing specific to the race. the cv joint would be the same. it's turned one direction for hundreds of thousands of miles, the grooves are mated to the wear patterns in the balls, the oil keeps everything lubed correctly, and the cleaning and re lubing gets any wear material that's developed over the years out. I vote to keep them on the original side.

They'll be wearing against an almost virgin surface on the opposite side. It's an old VW trick, when the CV joints wear out we could swap them and get lots more use out of them.

I posed this in another thread, but realized it really belongs in this one, especially in case anyone searching wants to follow the progress of this project:

The good news is, I got everything off and started to drop the subframe ... but, the back half won't drop. The bolts are all out, of course, but when I go to lower it, just the front lowers and hangs from the back. I tried gently coaxing the back mounts off the frame with a prybar, but didn't really want to go to town on it and damage something. Is there something I'm missing here? I don't think it's hung up on anything. Are the bushing sleeves just stuck to the frame posts maybe? If so, should I try torching them, or keep prying? I'm trying to be careful because I don't want it to suddenly pop free and crash down. Obviously I have the jack under it (plus an extra scissor jack) but still don't want any sudden lurches.
Help?

Use a second jack to support the front and keep it level, them lower the main jack an inch or two, then you can use the pry tool to lever the rear mounts. With the front hanging down it exerts off axis leverage on the rear mounts and the tubular studs they mount onto making it harder for them to disengage. Sometimes they will be stuck on there pretty firmly you just need to keep trying. A spray of KROIL to the top of the mount so that it can get on and leech down the stud can probably help some, and if you can get the tip of a bar, large screw driver, chisel in between the chassis and the mount where you can make some contact with its tip to the mount's inner/upper/central metal section into which the stub fits, giving it a "short, sharp, shot" or two, such a shock will help break it loose. The metal in the mounts are some alloy that can corrode and stick to the tubular stud's steel. This is the kind of stuff what "real wrenching" is all about! Good Luck!

Thanks, I think I was on the right path at least. :o I did think to push the front back up since it was making the rear mounts cockeyed, but it was still sticking so I wasn't sure if that was the right method. I'll shoot some Kroil on there before I go to work, then try again when I get home (or in the morning). I guess I need to be a bit less timid with the pry bar! I'll give a chisel a try too.:o
To be continued ...

I don't envy you. I spent a good deal of time beating on the one in my parts car, finally cut it out. The subframe still has the mounts in it, ... I soaked and pounded for a while until I lost interest, even tried a ball-joint press.

That's not too encouraging!:eek: Hopefully I'll have a bit more luck. I don't need to get the mounts out of the frame, since a "new" frame with new mounts is going on. But I can't cut the mount that's fixed to the car ... I'm gonna need that! I might try sticking the ball joint press I have in there ... it's about the right size.

Is BFH a b.. f...ing hammer?

Great
 

I'll give it a try. Thanks.

These are not going to come off. For anything. I am never going to finish this stupid project. Should I try firing the torch up bthe bottom of the mounts? I am prying with a huge prybar, and have also tried a chisel and a wood splitter with a big hammer. They don't break because the rubber gives and can't possibly exert enough force. And I can't seem to get anything onto the metal part of the bushing to avoid that.

That's where I decided to cut the thing out of my parts car, ... so I can't help you there.

I'd be starting to consider pouring a low durometer urethane into the bushing and leaving it there.

I think my next move, after studying an old bushing, is to cut the center of the bushing out. Which I'm sure will be a bear, but that way I can lower the frame off and put it to the side, then chisel -- or very carefully cut -- the bushing core off the post. If I could get a chisel tip on the metal part of the bushing, I think it would come off. There's not that much metal coming in contact with the post, but the rubber just won't allow enough force to be exerted to pop it loose. Unless I cut a hole in the trunk floor and stick a chisel down the top ... think I'll avoid that ... ;).
My big fear at this point is that I'm going to damage the post itself. Then I'm really, really up the creek. I guess you could weld one back on, but that sounds like it would be pretty unsafe. So I want to be careful not to damage the post or the threads.

Man! Wind is gusting to 50 here and its raining hard, but I went out and crawled under my tractor trailer box to get a first hand look at a nice clean South Carolina sub frame I've got there to refresh and get an idea of what things look like! Took a couple pics, sorry the one from below is a little blurry.

http://i470.photobucket.com/albums/r...emounts001.jpg

The one from above shows why that approach won't work; until you stretch the rubber enough you’ll never reach the mounts metal bushing. So forget that for now, although some penetrant in and onto the stud could only have helped.

From below does your view match this picture?

http://i470.photobucket.com/albums/r...ramemounts.jpg

If so that is where your efforts should be directed! It looks like the entire metal bushing is exposed. What you need to accomplish is to hit that hard with a decent hammer and punch/drift/chisel. You want to hit it so that you are rotating it around the tubular stud at its center. Give it a hard whack on one side and then the other, you just need it to break free and move a little. You want to direct your blows in the direction of the poorly drawn Chartreuse arrow points and attempt to get the mount to move in that rotation.

http://i470.photobucket.com/albums/r...memounts-1.jpg

Before doing that if you're worried about the subframe falling just reinstall a couple of the mount bolts, the other rear one and the diagonally opposite front one, that way it can't come crashing down. You don't need them turned all the way home just a couple rotations, clean any residual thread lock off before you do and it will make it a little easier, just be careful and make sure the bolts are straight and square you don't want any cross threading.

With everything secured try and hit the metal bushing to turn it, if you don’t get some results after the first ten or twenty hits, you could try heating the metal bushing with a torch, just have some water or an air blowgun at hand to keep things from getting out of hand and of course a fire extinguisher so you don't burn the place down. Get it hot, it doesn't need to be red or anything like that, just too hot to touch. Then give it the heavy hammer treatment again.

If by some chance you still are unsuccessful, you can destroy the metal bushing itself, hopefully you've got a decent drill and a cobalt bit or two. Depending in the size of the bit you have drill a hole or holes straight upwards in parallel with the tubular stud. I put a couple blue spots in the general place which appears to be the weakest part of the metal bushing where you would drill! That alone might do the trick, especially is you carefully wobble the spinning drill gouging the sided of the hole/holes some. If not after you've removed as much material as possible with the drill, it's time for a cold chisel and a hammer. Put the chisel across where you drilled and there are only webs of material holding it together and use the chisel to destroy the remaining webs.

If you have shop air a pneumatic impact hammer might well work in substitute for a swung hammer and chisel n both these methods, trying to turn/loosen the mount and later if need be splitting the mount off the stud. Usually Harbor Freight has them for around $10-15. I'd try it old school first, but your size and strength might not be enough and the air tool will allow you to use its power and your brain to get it done easier perhaps. Good Luck, don't get discouraged, this stuff is the real deal, anyone can change oil and brake pads! You’re doing great! When it gets time to install your nice pretty new rehabbed sub frame , are we going to slather the inside of those metal bushing and the outside of those tubular studs with Permatex Never-Seize? Your damn right we are!!!!

:P You better believe it! I want this to go a lot smoother when I do it again in 250,000 miles.:o
Thanks so much for the ideas ... I hadn't thought of using a punch to rotate the metal part. I tried whacking it from underneath just thinking it might knock something loose but, a side blow would probably help a lot more. That's why I thought sawing it apart might help ... but I'd much rather not enter that battle if I can get it loose while intact. I'll try it tomorrow!
I appreciate the encouragement ... it's so frustrating when one gets really, really close to completing a big step and then one little thing (or big thing) gets stuck! Then again I guess the more gets stuck, the more I learn about design and physics.:)

I tried hitting it rotationally a few times tonight, but it didn't budge. I'll try again tomorrow ... I didn't want to keep the neighbors away with incessant whamming at 1 a.m. I may have to resort to the drilling.
I think these mounts are trying to top the dreaded '78 UCA bolt for the Most Obnoxious Stuck Thing in my history of DIYing.

IIRC you had an air hammer around when you did the UCA bolt, this may be a good candidate for that treatment.

Another thought, are you swapping in a new (or should I say a more corrosion free) replacement subframe? If the old subframe is going to be scrapped you have lots of new possibilities for non-standard (read destructive) removal options.

Sawzall, cut-off wheel, plasma cutter, torch, ect, ect.

I ended up using a sawzall to cut into pieces that UCA bolt ... which may be what I do to the subframe bushings. I think I can cut through the two solid areas of the rubber and the frame should fall off. Then I can get a chisel on top of the metal core that's left on, and knock it off. The unnerving part is that I can't, of course, replace the post on the car's body. So I need to be really careful not to damage it. I don't need to worry about damaging the bushing or the subframe, since those are being replaced.:o