Thanks, Eric, for the reassuring words. After refilling the differential and buttoning everything up, I went for a drive (to take advantage of the oil filter sale at Pep Boys). When I returned home, the boots had popped out and looked completely normal.

Jeremy

Learnings from the axle job
 

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.

nice narrative. Now we want pictures, pictures!!:)

I will need to tackle that job pretty soon... but I dread it.

Thanks
 

Nice write-up!! Where was this when I did mine last month (all month long)
mine was stuck so don't forget LARGE brass drift :eek: . Too much heat on the Hub can Fry the wheelbearings. I also recived mine from CJ Axles along with above adivice. Thanks again ,

Good writeup, but, you fail to mention the process of actually removing the axle from the hub and the diff.

Some folks found the necessity to remove the shocks to get the wheel carrier down low enough so the distance between the carrier and the diff is increased to the maximum possible.........in order to get the splines to clear.

It appears that you had no need for that.......and the axles compressed sufficiently to simply remove them from the splines without any issues..........???:confused:

This is a job you can do! It's "crawling under the car dirty" but it isn't really difficult. Go slow, be careful, count your sponges (careless surgeons have been known to leave tools inside the patient) and do it!


And let me emphasize, seeing the picture, that my home-made Allen wrench substitute did not work -- it was not strong enough. Maybe if I had access to a welder....

Jeremy

Great write up. The drain plug can also be removed with an electric impact wrench. I say electric since air may well be too strong. When I did my axles last year I could not get the drin plug out so I gambled that I'd figure out something when the time came and took off the cover anyway. All it ended up taking was the impact wrench and about 15 seconds of running and it popped right out. Hex sockets are easily purchased on E-bay or through on-line tool sources.

You are correct, Brian. That's the problem with a "tale" as opposed to a "lesson." My story covered only the things I experienced and, as you have surmised, both axles slipped out without any trouble except for getting sticky goo (boot oil + duct tape stickum = goo) all over my rubber gloves.

The manuals do speak of driving the axle splines out of the wheel carrier (and being careful not to let the axle fall when it finally comes loose). However, I just pulled and they both came out easily. Next time, however, I suspect that the left axle may need help coming out, since I had a hard time getting it in.

I also read about lowering the trailing arms (disconnect the shocks) to get more clearance. That definitely requires disconnecting the brake calipers to prevent damaging the hoses. Again, however, I didn't have to do that. It was a tight fit (she said) but both axles came out with just a little wiggling.

When I stand back and look at the process as a whole, everything was in the preparation and the wrap-up. The actual "take out the axles and put in the new ones" was the work of only a few minutes. Hmmmm....I suppose there's a learning there, too.

Jeremy

More pictures
 

As usual, wish I'd taken more...

Caliper_4511 If you choose to unbolt the brake caliper, don't hang it by its hose as that risks damaging the hose. Use a piece of wire to suspend it from the sway bar. You can also set the caliper up on the shield behind the brake disk (red X in picture) where it is completely out of the way but use the wire, too, just in case it gets knocked off.

New_5425 This is a rebuilt axle from CVJ in Denver ($142 each + $50 refundable core each + shipping), in all its glory on the floor of the garage before installation. The axles are interchangeable -- the same part number fits left and right. The left side in the picture is the end that goes into the differential. The very end (arrow) is where the c-clip goes, after the axle is in the differential. The spacer that you removed from the old axle goes on the new axle at the point shown by the diagonal arrow BEFORE you put the axle into the differential. The smooth surface (arrows) next to the black "can" is the surface that touches the seal that lives in the side of the differential. Coat this surface and everything to the left of it, plus the seal itself, with 90 weight oil before assembly.

The early version of this axle -- goes back into the first W123s, I believe -- had fine grooves cut into the metal surface. This was to prevent oil seepage and is shown in the FSM. The later model axles do not have these grooves as the seal has been changed so that it prevents oil seepage. Most of us will never see this situation. Those who do can upgrade to the later axles (which all replacements are) and seals.

The right side in the picture is the end that goes into the wheel hub. The 8mm bolt (12mm in the older versions) goes into the end of this spline (arrow) after the axle is in the wheel hub. Coat the splines with oil to help them slide together. If you have an older version with the 12mm bolts, there is an upgrade kit to change to 8mm. [The old 12mm bolt has a much higher torque spec -- 70 ft-lbs. If you try to use this torque with a new 8mm bolt you risk snapping it off in the end of the axle. The torque for the 8mm bolt is only 22 ft-lbs.] If you get a replacement axle, it will be 8mm and you will need to get the new 8mm bolt, crush washer, and spacer. Torque the 8mm bolt to 22 ft-lbs. The crush washer is not supposed to be re-used as it keeps tension on the bolt. Since I had no new washers, I turned the old ones over. This is not recommended and I plan to buy new washers.

I had trouble with the outside spline on the left side of my car. The new axle's splines were a tad tight and didn't want to go in. There is a factory "assembly tool" shown in the FSM that can be used to draw the axle into the hub. I made my own by buying some longer 8mm bolts and a bunch of fender washers. I chose a bolt long enough to reach the tapped hole in the end of the axle, added some washers, and tightened the bolt, drawing the axle splines a little farther into the hub. (The tapped hole isn't very deep so you must be careful not to overdo it. When the bolt is tight enough that the hub starts to rotate, it's time to stop.) Then I added more washers and did it again. When the bolt ran out of threads, I switched to a shorter bolt. After four or five such procedures, the axle was far enough into the hub that the factory bolt could reach the tapped hole in the axle. Tightening that bolt pulled the axle all the way into the hub and I torqued it to 22 ft-lbs.

Bolts_4526 This is the box I used to hold bolts as I took them out. It's crude and dirty but it kept the bolts from getting lost and I was able to put each bolt back into the same hole it came out of. Some might think this is overkill but "the harder I work, the luckier I get." Left to right, the four groupings are:

1. These four hold the "rubber bearing" to the floor of the car. (The rubber bearing holds the back of the differential to the chassis. It attaches to the cover.) The factory says not to reuse these bolts, because they have sealant on them. I simply cleaned the threads and added new sealant.

2. Two big bolts attach the rubber bearing to the differential. They have washers and don't use sealing compound. Hint: when putting the rubber bearing back, attach it to the differential loosely with these two bolts. Then jack up the differential and attach the rubber bearing to the chassis with the four bolts #1. Torque these four to 22 ft-lbs, then go back and tighten and torque the two big ones to 88 ft-lbs.

3. The eight bolts hold the cover onto the differential. While you have the cover off, unscrew and clean the breather in solvent (only time this diesel used gasoline!) and replace it. Clean the sealing surfaces of the cover and the differential and put a film of silicone sealer on the cover. Inspect the differential one last time. Both c-clips in place? Remembered to put the spacers on the axles? Anything fall in the oil at the bottom of the differential? Then place the cover on the differential and screw in the eight bolts. Torque them to 33 ft-lbs.

4. The last four bolts hold the brake calipers to the hub -- two for each side. These are also "one use" bolts. I simply cleaned them, added fresh sealant, and torqued them to 66 ft-lbs. I'll go back after a week or so and re-torque them to make sure they're OK.

More learnings
 

Two weeks and 300 miles after the axle job. New sway bar links arrived. Good opportunity to install them and check underneath, see how things look.

Car on jack stands, start removing wheels. Hmmmm, first lug bolt isn't very tight. Hmmm, second lug bolt isn't very tight. Hmmmm.....realized I hadn't torqued them after lowering the car two weeks ago. All they had was the little bit of tightening I'd done with the car in the air, transmission in neutral and no emergency brake. Fortunately, none had come loose. I was lucky. "Kids, don't try this at home." :o

You bet they're tight now! 80 ft-lbs, every one. The link replacement was easy, a ten minute job, and everything else underneath looked good.

By the way, the 18 inch length of 1/2 inch iron pipe that I used as an extension for the 14 mm Allen wrench (differential drain/fill) stores nicely alongside the jack. Can't even see it's there.

Jeremy

Good common tools to have for this axle job
 

Some common tools would make this job quicker to do. Sears sells a seal puller for $9, looks like a short hook on the end of a straight bar, used a lot in transmission shops. Stocked in the automotive tools section of the bigger stores. I install seals with a 3/4 inch socket set, usually, although steel pipe caps fill in some of the in between sizes. Beat on the back of the socket with a hammer. Cheap sets are $99, if you damage the socket by pounding on it just file out the dings. For removing the 14mm drain plugs, I bought a set of SK allen adapters to 1/2 square, $85, the week I bought my car, and used a 600 ft lb air gun on the maximum setting. I found red transmission fluid in the diff, instead of GL5, so the money was worth it. I got my set at Ross Bros. transmission in Jeffersonville, IN, check the waiting rooms of car repair shops for flyers of vendors that sell this special stuff. Bent allen wrenches often need to be hit with a sledgehammer to do diff and transmission plugs, and usually you need a 3rd hand to hold a hammerhead against the wrench to keep it from twisting out while you hit it.

Great Write Up - what other parts do I need?
 

Thanks for this great thread, just about to undertake this job empowered by the info here...

Ordered my axles from CVJ. They did not have them in stock, rebuilt them and shipped in two days.

Jeremy5848, can you list the parts you needed to purchase in addition to the axles? You mentioned new diff seals and washers (as well as bolts that you re-loctited). Any other 'good idea to fix while youre there' parts?

Ill take some more pictures when I do the job to supplement.

Thanks!

The side cover (output) seals in the differential were bought from a local foreign car parts place (Smothers) here in Santa Rosa. I waved my hands and they looked in their computer and came up with their part number "MER 0039978347 Final Drive Seal." They had to order them but I was able to pick them up 24 hours later. Two seals and tax cost me $16.57. They were perfect matches for the old seals. I'm sure you can get them from Phil. I would have gone that route but was in a hurry. I don't have the factory part numbers. I made an install tool from ABS pipe; others have used a big socket. The factory has a special tool (of course).

An important note: the early design of the W123 cars (and probably others) called for spiral grooves to be worn into the end of the axle to keep oil from leaking through the seal. The later seal has a design that makes the grooves unnecessary. This is discussed in the FSM. It would be possibly to buy bargain seals that turned out to be the old design. Be careful. I wish I had a photo of the lip of the seal, showing the lines. The FSM shows them, I think.

The bolt, spacer, and washer that hold the axle to the brake hub may be reused. Mercedes uses a strange name (I forget) that doesn't sound at all like it might be a washer. I turned mine over and reused it. Next time it should probably be replaced. The metal will eventually become brittle.

I also replaced the rear sway bar links because they needed replacing and I was in the area, so to speak. Check the rear brake pads and rotors, also the emergency brake hardware. Look for leaking brake hoses and also for leaking fuel tank to steel fuel line hoses. Make sure all of the body drains that empty under the back of the car are clear. There are also some rubber parts that are part of the subframe but I'm not qualified so didn't look. Others have mentioned some rubber parts in the drive shaft as well as a diff input seal.

Make sure you clean the sealing surfaces of the diff and the cover really well and make sure there are no burrs. The silicone sealant (any kind) that is used is the only seal -- no gasket. After cleaning, wipe down the surfaces with alcohol to remove any remaining oil or grease.

Ditto on cleaning the drain and fill plugs. I used teflon tape, not sure if it was really necessary. Anti-seize might be a better idea, especially for the fill plug, which is a steel plug in an aluminum cover.

Take your time. Clean underneath first. Support the car securely. "Measure twice, cut once." The axles aren't terribly heavy but if one end comes loose unexpectedly, damage to you or to the diff can result. Put oil on the new side seals before you drive them in and before you insert the axles. Don't lose the clips. Remember the spacing washer, take it off of the old axle and put it on the new one, don't confuse left and right spacers, they may be different thickness.

The factory recommends replacing the four bolts that hold the diff carrier to the floor of the car. That is apparently because they don't trust people to remember to clean off the old bolts and add new blue Loc-Tite. The bolts don't stretch in use so there is no reason to not re-use an undamaged original. Same for the brake caliper bolts (two per caliper) if you decide to remove them (makes getting at the outside end of the axle easier). Don't let the calipers hang from the hoses. Use a piece of wire as a hanger. I also found that the caliper would sit up out of the way on the shield. See photo. I left the wire hanger on, just in case.

PN's
 

jeremy 4858,

Got my axles and am ready to go. Just talked to Phil and I couldn't get a part # for the washer you have talked about simply becuase I'm not familiar enough to descibe it to him.

does the FSM give you a PN? my CD FSM doesn't have the axle replacement article yours must...bummer.

-dd

Axle
 

My paper FSM and CD-ROM FSM have the same description of the axle job. The big crush washer on the outside is called a "clamping disc." Strange term and note the use of a "c" in "disc." No part number. I guess you need a parts book for that. I reused the old one, most people do, my indy said to turn it over and bend it the other way.

No problems so far, 7000 miles on since the work. Only thing I've done since is to drain the dino oil from the differential and put in Mobil 1 75W-90. No noticeable difference.

Jeremy