Differential mount replacement procedure, 300E
 

I have ordered new differential mounts for my 300E. My main concern is replacement of the two in the top, rear of the differential.

It seems that the outer part of the bushing is a press fit into the crossmember holes. This outer part is sheet metal thickness, and it looks as if I can air chisel it out easy enough, but how tough will it be to get the new one in place? Will I be able to drive it in place using a block of wood to protect it, or is it truly a press fit?

Thanks for your help,

Larry,

I had a Baum available when I did this job. Its removes and installs. For the install, one side went in from the rear of the subframe towards the back of the car, the other and it would just start to go in at an angle (twice) - so I installed it from towards the front of the car. It was a tight fit. My
regular' mechanic told me (he does not have the tooll) he cuts the outer sheetmetal so it will compress a bit, then drives it in with a hammer.

The shop manual specifically mentions a procedure for 'squaring' up the diff. using a special jig. I am not sure what happens if this is not followed, but I carefully installed the bushings to the same position of the old ones. Not sure if an air hammer would give you this precision.

I used an air hammer to help remove my support joints. In that case, the Baum tool I had available wouldn't work either - at first. I used an air hammer on them (which didn't move them any noticable distance), but it must have freed up a 'bond' because then the Baum tool did its job and the joint pressed out.

I hope my indirect experiences are of some help.

Thanks for the reply.

I was only talking about using the air hammer with a chisel to remove the old bushings. I was assuming I could drive the new ones in with a hammer. Can I indeed drive in the new bushing with a hammer?

Thanks again,

I've heard that cutting the sheetmetal with a hack saw or equivalent and then driving it in with a hammer works (from my mechanic, but have no personal experience with this method). Also easier if you grease the metal. Its a tight fit. The only other person I know that did this (without the tool and without cutting the bushing) said it took two days and a lot of cussing and he would just paid somebody to do it next time, or he would take the subframe out and use a press... You may be able to fabricate a puller, pusher with some sockets washers and bolts.

Did you have much slop in the differential gears?

And is the differential loose in its mounts?

I'm just wondering if you're replacing the mounts based on rubber appearance, metal-to-metal contact, obvious movement, etc. so I'll know what to check for in the future.

Ken300D

Hi Ken,

When they go bad the differential will be loose in its mounts. - e.g. try turning one of those 12 mm bolts and see if the diff is well supported or move around. Tends to also make a klunking noise when loads are changed. Be sure to install the mounts with the correct orientation they are not symmetric.

They are most definitely shot. Yes, you can see that they must be installed with the correct orientation.

Thanks for the replies,

What is a Baum??

Should have said "a Baum tool". They make speciality tools, alternatives to the dealer tools for a particular job. For example, Baum sells the differential bushing tool for about $96. AST (Assenmacher Specialty Tools) also makes specialty tools.

Larry,
You cannot install those bushings with a hammer. My first attempt I tried...and failed. It's definitely a press fit. The right tool is a bolt with the right size cup and washer to push/pull the bushings without damage.

The other option (which I used) is to remove the whole subframe and use a shop press. In my case, I bought a 12-ton unit from Harbor Freight for around $100. I replaced every bushing and all the arms.

Larry,

I did this a while ago and wrote up my approach:

http://www.peachparts.com/shopforum/tech-help/23292-differential-mounts-follow-up.html

I tried the air hammer to knock the old bushings out, but I could see that I would end up boogering up the subframe. The problem is that the bushing shell is very thin and you can't get a good surface to hammer against without banging the subframe too.

The push/pull tool is the way to go. Wait until you hear the thing pop when it breaks free! They are in there very well and you really need to apply even pressure around the entire diameter to get it out without doing other damage.

Hope this helps.

Well, after learning more about what's involved, I talked to my brother in law at the MB dealership. He has a tool that he made on his metal lathe. No one in the shop owns an MB version of the tool and they borrow his. He offered to loan it to me.

Thanks for all the replies.