W124 Differential mount bushing replacement
 

So, I am going to undertake this job shortly, either this weekend or next, all depends on how the following questions are asked. I figure I might as well make it a DIY as well, just for fun.


The questions...

Should I unbolt the half shafts from the differential? I read somewhere that those bolts are one time use and They appear to be XZN (triple square), correct me if I am wrong.

Does it help to remove the back portion of the exhaust. The connection point is right at the differential pumpkin and looks like its an easy unbolt/bolt job.

Can I reuse the bolts for the differential mount(s). This includes the two 12mm allen cap bolts and the one 8mm allen cap bolt with 17mm nut.

Can someone give me a tip or trick to hold that 17mm nut, it's in a pita location.



Other than that I have the correct tool to remove/install the bushings and all 4 bushings. My two differential bushings on the rear of the differential are very very bad looking, the other two up front are ok but should be replaced.


please chime in if you can help.

thanks

If you're going to drop thr diff down and out completely, yes.
If you are going to try and squeeze the tool in between the diff and the sub frame, no. Early bolts can be Allens, later can be XZN, and even later can be male TORX. Reapply blue thread lock is fine, they are not single use stretch bolts, but MB recommends replacing not reusing many bolts i. e. caliper bolts.

You can separate it but it's a slip joint so it can be a bear to get it apart and the clamp deforms the pipe. But you can ubfasten it at the hanger at the muffler and the one at the subframe and let it hang down to get the room you need,

You can reuse each of those bolts if they are not rusted, the 8 mm is often rusted on the nub that extends past the nut.

You can get a Sears 17 mm 3/8" swivel socket on it and use a 6" 3/8" extension attached as a handle or get a cheaper sacrificial 17 mm box wrench that you can bend to get on it but the box end needs to be pretty thin as there is not much space between the nut and the indent in the subframe that surrounds it. It is best to use a penetrant a day or two before and when you tacle that bolt/nut have a helper who can concentrate on holding the nut straight square and secure and the other person concentrate on holding the Allen tool in the bolt head srtaight, square and secure. It is easy to strip the 8 mm Allen head bolt. Put the Allen tool in the bolt head and give it a couple sharp whacks with a hammer to help break any rust free befor you try to turn it.

Disconnect the ABS sensor inside the cabin behind the rear seat cushions and push the wire pigtail and the rubber grommet out through the hole, disconnect the grommet on the subframe to achieve more play in that wire pigtail. Dont fool with the ABS sensor it can be very difficult to remove, its 5 mm bolt strips out easily, if you remove it from the diff you will need a very very thin specific O-ring to reseal it and prevent its leaking.

If your doing this on your back have your assortment of jacks available to catch, support and manuver the diff back into position, it's a punkin a very heavy hard to grip steel punkin coverd with grease and grime!

Get the two rear bolts started but leave them loose and then get the front mount lined up and the bolt and nut threaded befor tightening anything up, you'll need to move things around to get it back in there tightened up.

A thin box wrench makes disconnecting the flex disk from the diff much easier for the bolts and nuts on that the nuts are 17 mm the bolt heads 15 mm if I remember correctly.

I guess I will call my parts guy and cancel my order of those two 12mm allen cap bolts since mine are fine. I had to clean the inside of the head out to insert the allen socket

I already hit the allen head with my cordless impact just to see if I could get it to spin so using the ratchet would be easier.


I only ask about removing the half shafts because it looks like that would allow for ample room to use the bushing press tool.I'd like to not remove the half shafts


How do you know about the 3/8th swivel? Guessing you've done it before.

I've always done the job under lift with hydraulic transmission lift at assist so it's easier to just use an impact wrench with a long extension to disconnect the axles then completely drop the diff downward and forward enough to get the bushing tool in and out. Some people have claimed they've done the bushing R&R without doing that just disconnecting the drivesaft and mounts and moving the diff enough out of the way to get the tool ing and out, I hear that but can't see that happening.

When I spoke aboud the forward mount bolt I maybe wasn't clear I put the Allen tool into the bolt head and strike the tool into the bolt head to impact a jar the bolt and nut connection in the hope that it would help break the rust and corrision free a bit. Because the nut is in such a peculiar position and therefore difficult to get a good secure grip on it the usual tricks that could help free a difficult fastener are in order. I don't recall off hand if that bolt is thread locked but if it is heating it a bit with a torch can make all the difference between a "yeah, it's moving and damn I just can't get tools on it good enough to apply enough force to breal it free". When doing this work sometimes there is not much difference between a hard job and a ball breaker job other than one fastener that just won't yield.

I've done the task numerous times and the swivel socket not a swivel and a socket is the easiest to get it done, there is not much room for a longer wrench to avoid the subframe or underside and get on the nut. With the swivel socket you use it with the extension where it is used with greater than a 90 degree angle almost U shaped with the socket on the nut verticle and the extension handle sloping off to and angle and downwards. That's why having someone else helping concentrating on holding the counterforce is best, the problem is always just getting it to break free, once that's accomplished it's a piece of cake!

1st source I check is gsxr
 

"W124 Differential mount bushing replacement "

I do hope my sears has the swivel socket in stock, I can see how it would be useful.

Maybe they have the full set that could be returned after you discovered it was "not as useful as you'd imagined"

Maybe....but it's an excuse for new tools.

I believe I'll need the triple square bit. A search shows 10MM. $8 for a stubby xzn on amazon. Done

The axle flange bolt are 10 mm XZN probably, but check for certain could be Allens or even male TORX. You should check with the MB Dealership for the XZN M10 as they sell a HAZET tool with the MB part number etched into it for less than $20, the Snap On equivalent will be at least $45 or $50 and the cheapo ones from AutoZone will be $10 but if you get through removing and reinstalling all 12 axle bolts you'd be lucky. The XZN M10 is also the OM 60X cylinder head bolt size and its the alternator shaft counter hold size as well a a few of the rear suspension links bolt head size so it's a tool that might get some use if you work on your car over the next couple years.

The dealer in my area would over charge for it.

I think the axle flange bolts are smaller... 8mm or the head bolts are larger, 12mm?

Having worked on a couple dozen of 124 vehicle's axles I've only seen three likely possibilities; early 8 mm Allen, later XZN M10, latest male TORX not certain of the specific size designation.

The cylinder head bolts for the OM 60X family of engines is XZN M10 with the exception of two Allen head bolts located at the front of the engine in the timing chain chase, the OM 61X family of engines cylinder head bolts are XZN M12.

I'd still check with the dealer on the tool you might be suprised, the tool lists for about $50 -60 elsewhere on the web.

All credits to GSXR
 

Mercedes part # 601 589 00 10 00

Retail $20.40 @ MB of Napierville AKA XXXX

[Zomeone bought one from MB CinCiny for 18.50 USD about 4 YAG.]

Oh, and
Robert,
http://www.w124performance.com/

the local dealer is known to have insane markup and also charge shipping for small parts (I'm usually never charged shipping for small parts to the dealership by my usual place)


I ordered a 3/8 drive 10M XZN from amazon. I'll just stick it on an extension to remove the bolts. Maybe later I'll order the proper hazet XZN from my parts guy, but the amazon socket has great reviews.


FSM mentions to drain the differential before removal. I do have a jug of synthetic diff fluid I can use to refil it once its back in and I probably should drain and fill it anyways since it is weeping a bit.