PeachParts Mercedes-Benz Forum - W123 axle R&R job--some questions?

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Great thread. I followed the guidance here and all went well. The only point I will add is that when fitting the axle stub to the hub, jack the differential all the way up to provide the play needed to fit the splined axle hub to the wheel hub. Also, if you use the lug bolts to hold the rotor on while you secure the caliper the lug bolts will allow the hub 1/4 turn only. No, you didn't screw the job up. Remove the lug bolts, put the tire on and give it a go!

Another note on your Allen socket: Harbor Freight sells a whole set of Allen sockets, including the commonly-used 4mm, 5mm, 10mm, 14mm, and 17mm sizes for only $13. (Those aren't the only sizes it contains.)
Comes with one of those nice socket-holding hand bars, too.

Quote:

Originally Posted by yogarda (Post 1749142)

And they even held up being used with an electric impact wrench. That was how I got the plug out of the housing cover. I've had good luck with some of their tools.

This is an awesome post. Thanks for taking the time to write everything up. I think I'll be just replacing the boots on my 82 240d. Does anyone know what the grease that goes inside the boots is and where to get it?

When I was limping back through Nevada with a torn boot, I was able to buy CV joint grease at a chain auto parts store. "Split boot kits" usually come with a packet of grease, too. I suspect that in an emergency any kind of grease would do. (Mercedes uses a kind of oil, at least that's what dripped out when the boot first tore.)

Jeremy

I'm setting up to do this job today.

I have new axles, not remans, and the notes on the box say
to remove only one axle at a time because if you remove both,
"side gears may lose alignment".

Is this more of a generic warning, or does this apply to our diffs?

Quote:

Originally Posted by techguy512 (Post 1799993)

It must be a generic warning. You can certainly remove both axles simultaneously on a W-123 or a W-126.

Completed the Job

I completed this job today.

Biggest hassle was getting the c-clips reinstalled, and getting the old axle seals out of the diff housing.

I found one shim, on the passenger side. Could not find any on the left.

Getting the splined ends into the hubs was interesting. I thought I was going to need to drop the trailing arms, since there was a tiny fraction of an inch on each side that I couldn't clear. However, messing around with it (like a puzzle) led me eventually to a different angle of approach where the end cleared easily. Lesson is don't give up, and try different angles until you find one that works.

Shifting in an out of gear is much smoother, with less body bounce which I attribute to the new rear subframe mount.

All in all, a 5 out of 10 in difficulty.

Quote:

Originally Posted by Jeremy5848 (Post 1206682)

Here is what I learned from replacing the axles of my 1985 Mercedes 300D Turbo (the boots were torn). Many of these learnings came from reading this forum. Implied thanks to all who unselfishly donated their hard-earned knowledge. "How-to-do-it" has been posted by others previously; this is a "rest of the story" story. Caveat: this is how I did the job. Your mileage may be different.

This is definitely a job that most of us can do. It doesn't take any special tools or knowledge beyond common sense and can save you a pile of money, especially if your mechanic is expensive and wants to use new parts from Mercedes.

1. You don't need a lot of tools and supplies
Pair of jack stands and wheel chocks
Metric 1/2 inch drive socket set
Torque wrench
Pry bar (18 inch minimum) for removing old seals
Snap-ring pliers or other hooked device for axle c-ring
14mm Allen wench with 24" extension (pipe) for the differential plugs
Propane torch in case the differential plugs are really tight
Drain pan
Work lights
Rags (lots)
Teflon tape for drain and fill plugs
90 weight gear oil
Loc-tite or similar thread-sealing compound (the blue kind)
Silicone sealant for differential cover

2. Preparation is important. If possible, degrease and pressure-wash the underside of the car. If your axle boots are leaking like mine were, the underside of the car will be coated with oil. A clean, flat place to do the work is nice. You'll be spending a lot of time on your back under the car. Be sure to chock the front wheels securely; they are the only things keeping the car from rolling (especially important if your site has an incline). Try to have everything you need beforehand and don't start without the big Allen wrench like I did (and then discover that most stores carry up to 10mm only).

3. I used an old cardboard box as a bolt holder, making simple drawings on the box and punching holes for each bolt. That way, each bolt went back into the same hole.

4. The factory recommends new bolts for the brake calipers and for attaching the "rubber bearing" to the floor of the car. However, this is only because the bolts have locking compound on them. All you have to do is to get some Loc-tite or a similar fluid (the blue kind) and you can clean and reuse the old bolts. The 8mm bolt that holds the axle to the wheel hub uses a cupped washer that the factory calls a "clamping disc." This washer distorts when torqued and is supposed to be used once only. Since I did not have new washers, I turned the old ones over. I do plan to replace these washers, since they are easy to get at.

5. Removal of the brake calipers is necessary only if you have trouble getting the axles out and have to lower the semi-trailing arm (by unbolting the shock absorber) to get more clearance. (I didn't have to do that.) However, it is handy to have the calipers out of the way so you can see better. The books recommend hanging the caliper with a piece of wire (saves the brake hose) and I also found that I could put the caliper up on top of the wheel hub where it is out of the way.

6. The drain and fill plugs in the differential may be tight. Make sure you can get the fill plug out before removing the drain plug. The fill plug is steel, screwed into the aluminum cover of the differential, and is especially prone to sticking. I ended up using a torch to warm the cover before the plug would break free, even with a two-foot piece of 1/2 inch steel pipe as an extension for the 14mm Allen wrench. I put Teflon tape on the plugs before I put them back; maybe it will help get them out next time.

7. When you pull the c-ring off of the inner end of the axle (inside the differential), it will probably go flying. Covering the differential with a shop rag will keep the ring from ending up in the next ZIP code. When I put the c-ring into the new axle, I used a pair of needle-nose pliers to get it started into the groove and then drove it home with a pin punch and a small hammer. This is a personal choice; use what works for you.

8. You don't have to replace the seals in the side of the differential (each axle goes through one) but it's a good idea. The left one in my differential showed signs that it was starting to leak. They were only six or seven dollars each. The FSM and Haynes both have this cute picture of the old seal being levered out with a long screwdriver. This is a joke. The seal is made of much sterner stuff and laughs at mere screwdrivers. I used an 18 inch wrecking bar and both feet.

9. Installing the new seals is not difficult. Lacking the factory tool (of course), I made one from a short piece of 3-inch ABS plastic pipe (the black stuff used for drains). If you sand or file the inside diameter a little, it will fit perfectly over the rubber lip on the seal. I put a cap on the other end of the pipe and gently hammered on it to drive the seal into its space in the differential. Putting a little oil on the outside of the seal helps it go in smoothly. The ABS pipe is slightly larger than the seal and stops when it hits the side of the differential. This turns out to be exactly what the factory tool does -- the seal is now properly seated.

10. There's a lot on this forum about replacement axles. Replacing the torn boots is possible, although special tools are required for the factory boots. An after-market "Flexx" boot is available although the special air-operated "Flexx-gun" is $250 unless you can find one on eBay or know a shop that will do the job for you. The Flexx boots are made from thinner rubber than the factory boots and will not last as long (ten years instead of twenty?). This is probably the least expensive way to go if you're short on cash. Since my axles had over 200,000 miles on them (1500 with torn boots), I decided to replace them. Rebuilt axles are available from many sources with prices under $100 but posters to this forum have reported mixed results. The least expensive new axle I found was $400 (each). In the end, I chose the rebuilt axle sold by CVJ of Denver for $142 each plus a $50 refundable core charge and shipping (40 pounds total). They have most axles in stock and can build one for you in a day or two if yours isn't on the shelf. I called them on a Tuesday and had the axles the following Monday.

11. The shim or spacer on the differential end of the axle must not be forgotten. When I removed the old axles, one spacer came out on the axle and the other stuck in the differential. The spacers are sized for the differential and each must go back into the same side. If the axle builder has done his job correctly, the axle will go into the differential, leaving just enough room for the c-ring to slide into its groove.

12. Remember to lube the splines and the new seal in the differential to help the axle go in smoothly and not damage the new seal. I had trouble getting the left axle to slide into the wheel hub, as the splines were very tight. I ended up buying some long 8mm bolts and used them to slowly draw the axle into the hub. Heating the hub with a heat gun, being careful not to damage the seal, might also have helped but that was a "next step" that I didn't need to take.

13. Once everything was back together, I refilled the differential. I used an oil pump container that I bought many years ago for filling BMW motorcycle transmissions. All I had to do is pump until the differential started to overflow, then removed the hose and screwed in the plug.

14. Before I took the car off of the jack stands, I started the engine and put the transmission in "Drive" for a few minutes, to make sure there were no bad noises or leaks.

15. After a week or so, I'll check all of the bolts to be sure they are still tight.

Thank you Jeremy for your thoughtful and exhaustive work. I have done this job three times and have a few additional tips to add. The idea to use 3" ABS pipe is good but I had to chamfer the inner edge with a rotary rasp to get a perfect fit. I don't have a lift and I couldn't get enough swing room on the driver's side axle to really drive the seal in far enough. I had to finish tapping with a hardwood block on the outer edge. To get the seals out I also had to use a long crowbar and hit it hard with a small hand sledge. Careful not to go to far in and score the inner race. Second tip is to get the clearance necessary to get the wheel side splines in you normally have to remove the back seat and disconnect the shocks to let the trailing arm drop a bit more. A quicker way I just discovered is to use a bottle jack and raise the differential JUST ENOUGH to allow the splines clearance. Slick, simple, and quick.You also have to collapse(Compress or shorten the axle) To ensure that the splines go in on the wheel assembly I think it a good idea to dress them up to remove surface rust as well as the axle end, Make sure there are NO DINGs or you will have hell to pay. Coating both with a little spray oil and they slip in with ease. A little tapping on the can flange can help to get the last inch. Don't tap too hard on the somewhat fragile cans. I had a MB mechanic do this 3 years ago and they charged me $690 to do just one side.On my last job I used 2 junkyard axles with low miles and intact boots. They were $100 each. Low milage used axles are preferable IMO if you can find them. If the boots stay intact these are very durable units probably good for 4 or 500 K miles.

Quote:

Originally Posted by HughO (Post 1824930)

...The idea to use 3" ABS pipe is good but I had to chamfer the inner edge with a rotary rasp to get a perfect fit....

I did that too, didn't put it in the write-up because it was already too long and I frankly didn't expect anyone to try that idea. But it's good to hear that someone did and that it worked for you too.

I read that in some cars it's necessary to disconnect the shock so that the outside end of the axle can be lowered farther. I found that raising the diff with a bottle jack gave me enough room. My only concern was the bottle jack slipping because the bottom of the diff is slightly slanted.

Thanks for the kind words. :D

Jeremy

Jeremy5848 & Others,

Thanks a ton for all the helpful info. Today I decided to go for it - replacing my passenger side rear axle. It took me about 10 hours to get the part from Pick-n-Pull, and install it myself, it made me happy to have a running car by the time the sun set!

The most difficult part was removing and installing the c-clip. To those who are going to do this repair, I suggest buying the screwdriver hook tool or similar device mentioned on this diy. I used a piece of tie wire with eventual success.

Again, thanks for all the helpful info and ideas.

-John Paul

Quote:

Originally Posted by JohnPaul (Post 1979048)

Nice job John. Feels good don't it! That is a repair/replacement that really makes you feel like you've accomplished something. ;)

I too want to say WHAT A GREAT THREAD. I have a few questions.
I have a '84 300SD. Is this process the same for my 126 car?
Where can I get the tension / clamping disc washers.
Where can I get the final drive differental seals?
I would like to use the funnel method to install boots. Would like to get
axle to practice on. The YouTube videos show that it can be done.
THANKS

Ryan,

You have a couple options for parts procurement:

1.) Call Phil at this site. He will be able to get you the parts no problem.

OR

2.) Sign up for a Mercedes Parts Catalog account at www.startekinfo.com/epc. That way you can browse the parts #'s yourself using the VIN from your 126. You can then order through a mercedes dealer, this site, or most parts counters like say CarQuest.

dd

The "clamping disks" are available from Mercedes dealers and as DieselDan says, Phil should be able to get them for you too. I'm not sure how critical they are, I just turned mine over and reused them. The metal should stand up to a certain amount of re-bending until it starts to crystallize.

The side seals in the differential should be available from "foreign car" auto parts places and that will save you some money over dealer prices. I was able to get them ($16.57 for two including tax) by simply telling the parts guy my make and model. In a pinch, you might have to take an old seal in for comparison – not ideal, since the car is down while they get the seal.

Jeremy