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Old 09-10-2001, 03:40 PM
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Join Date: Jun 2001
Location: California
Posts: 327
Thumbs up Differential Mounts: Follow-up

Thanks to J. Hidalgo for warning me that the differential mounts were not a simple job.

While they certainly weren't simple, I didn't have too much trouble, and my home-grown puller/installation tools did just fine. Since a lot of others have asked questions about this and it's all fresh in my mind, I'll try to outline the installation. FYI, I would consider this to be a DIY job only for advanced DIYers. If you're a white collar worker like me, don't do it the day before a big meeting! It is a filthy, messy job if the underside of your car looks like mine! I tried to wear gloves, but the best way to tackle it was to just go for it. If you've done this job, then this write-up will make sense. If you are considering it, then I hope this helps you decide if it's something you want to tackle.

The car: My car is a 1994 E320, but the mounts on my wife's 1990 300E look the same and this installation is probably the same for many many years and models.

The symptoms: My car had a clunk when I chopped the throttle and a quick visual inspection showed that the driver's side differential mount was shot. I could see that the rubber cushioning the inner mount from the outter "shell" was torn and much of it was missing.

The cure: I bought the mounts locally for $11.50 each. Sorry Fastlane... next time... For the puller/installation tool I dropped by my local industrial hardware supply shop and bought:

3 feet of 1/2 x 20 fine thread rod
2 (grade 8) 1/2x20 nuts
An assortment of washers
A 2 1/2 " cast iron pipe cap

I also went to Sears and bought a 1 1/4 " 3/4 drive socket. This socket had an OD that was slightly smaller than the bushing (about .001") and was the key to pushing the old bushings out.

Okay, I supperted the car on jackstands and let the suspension hang freely. I took off the rear and mid exhaust supports and let the pipes hang (I put a couple of wood blocks about mid-way to support the weight) I used a 12 mm hex bit to remove the two big bolts from the back and an 8 mm hex bit on a 3/8 drive extension for the forward mount. There is a 17 mm nut on top and this is where you decide to shed the gloves and just reach up there to feel what's going on!! I had to take off the fuel pump cover to get the driveshaft safety loop off. I lowered the differential as far as it would go to gain access to the bushings.

I drilled (bored) a 1/2 " hole in the center of the pipe cap and this served as the cup that I pushed the old bushing into. I cut a section of the 1/2" threaded rod and slathered everything in Mobil 1 oil so nothing would gall when I started applying pressure. I had considered getting a roller thrust bearing like the one you would use on a harmonic ballancer installation tool, but I didn't and it went just fine. Well, the hard part was getting the old bushings out. They were "Grown" in there. It's just a matter of configuring your puller a few different ways until you get them to move. Drawing the new ones in is easy, and if you've gotten the old ones out, then consider yourself experienced! Make sure you change them one at a time so you can compare the one you are installing to the other one. You need to have it configured correctly and also you need to draw it into the hole to the same depth (there is no stop).

The bottom line: I spent about $20 on my makeshift tools. I think the correct tool would certaily make the job easier, but this is a tough job no matter what you do. My car feels new again. This repair did not just correct the clunk, but the responsiveness and overall feel are significantly improved.

I hope this is useful for someone. I spent about 2 1/2 hours on this, but I think I could shave at least 30 minutes off if I did it again. I suggest this for advanced DIYers only.

Good Luck!

Last edited by 300EE320; 09-11-2001 at 12:23 PM.
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Old 09-10-2001, 10:49 PM
J.HIDALGO's Avatar
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Join Date: Jul 1999
Location: Jax, FL
Posts: 1,785
Red face I told you...

Congratulations! and I am glad everything worked out for you. It is a pleasure to work on MB's (sometimes dirty) but, they are built so well. As you noticed, most parts are not expensive compared with some japanese and american cars. Labor, on the other hand, is much more expensive.
They are things better left to the pros but, they are many things I can do and enjoy doing them myself, just like you.
I know exactly how you felt once you completed the job. There is no price for that feeling (at least in my book) and, a lot of people in this forum know exactly what I am talking about...don't you guys?
'86 300E
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Old 09-11-2001, 02:29 AM
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Join Date: Apr 2000
Posts: 412
Way to go Dude! I will be replacing my mounts and fabricating my own tools also. The prices that they want for these special tools is obscene. I have fabrcicated a tool for pulling axles out of front wheel drive cars that works quite well. Maybe it will make me rich someday.
I must say that a plumber friend of mine will cut the pipes for me to make my tools to press out the subframe bushings.
1990 190E 2.6
1996 Grand Voyager 3.3
1985 Mustang GT 5.0 5 SPD
1982 Suzuki GS 750T
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Old 09-11-2001, 06:20 PM
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Join Date: Jun 2001
Location: California
Posts: 327
Thanks guys!

I think that a 2" section of 2 1/2" pipe would have been a little better than the cap I used.

One thing I can't stress enough is to get thick, heavy washers to pull against. I thought mine were thick enough, but they bent anyway. I had to dig into my junk box and find some heavier washers.

Overall it's a fun job if you have the right expectation. A little tool fabrication, some strategy, and yes, as J.H. put is, a rewarding feeling when it's done.

What will I do with all the money I saved...:p

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Old 09-14-2001, 05:00 PM
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Join Date: Aug 2001
Location: Florida
Posts: 272
It shouldn't surprise me when I find something discussed here I think is obscure. I have a 92 400E with a distinct thunk when I accelerate in a manner to which the car feels appreciated. Anyway I have been wondering what to do about it and happened across your thread. With your permission I have printed it and will give it a try. I have done all the work on my cars for most of my life (the benefit of my father being a mechanic his entire life) even though I'm a white collar warrior. Anyway had to comment in way of appreciation of the time you gave to explain the proceedure.
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Old 09-14-2001, 07:30 PM
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Location: California
Posts: 327
Hi Brian,

You're welcome! The comments I've received have been well worth the time I spent writing it up. When I did a search, I saw that others had been asking about this, so I'm glad to share my experience on it.

04 ML500
02 E430

Experience is something you don't get until just after you need it.
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Old 12-10-2001, 12:33 AM
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Join Date: Jun 2001
Posts: 69
Whew!!! What a PITA!!!

Well, I have just spent practically two days underneath my 300CE... and now all the work is done and well worth it!

When I got the parts from Phil, I thought that the front and flex disc removal and installation would be the hardest. In fact I hardly spent 3 hours for both. The differential mounts were another matter.

Before I began, I made sure that I researched the procedure so I could be more efficient. I got the appropriate tools (or so I thought), and ripped right in. It wasn't as easy as it seemed however, since I wasted roughly 3 hours going to the hardware and auto parts store to get the right parts. I know, I know... you described the fabricated tool in detail, but I thought it would be easy to pull the remnants of the old mount. Boy, was I mistaken! The whole ordeal must've been 4-5 hours of agony!

ANyway, it's all done. Thanks everyone for the help!
89 300CE
91 Supercharged Miata
99 E320 Wagon
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Old 12-10-2001, 12:46 PM
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Join Date: Jun 2001
Location: California
Posts: 327
Great job Squid!

When I researched this I came across one of the threads from a tech who said something like "we just hammer them out". I'd sure like to see that! I can't imagine smacking it that hard with a hammer and not damaging something! I think you characterized it correctly - PITA.

It's such a simple job (conceptually), but is mechanically challenging at the same time.

04 ML500
02 E430

Experience is something you don't get until just after you need it.
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Old 02-20-2005, 01:23 PM
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Join Date: Oct 2004
Location: San Diego, Ca
Posts: 24
Hey Dennis,
Great write-up. Just completed the job and the car handles way better. My mounts were totally shot. Looking at the new mounts, the logic of construction seems a little off. It seems to me if the mount was a solid rubber bushing inside it would last a lot longer.

A bit of advice too add, use a 2" diameter pipe nipple that is approximately 1" long. You will probably have to cut it in half. I could not get the driver side mount out because there was not enough room for the 2" long pipe nipple. I also found these really heavy duty square washers fron Home Depot. Theyr'e 1/4" think. I found it easier to use the socket to initially start pushing the bushing out, then use the new bushing to push the old one out. Make sure to rub antiseize on the new bushing, and use the square washer to press it in.

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Old 02-20-2005, 08:35 PM
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I did this job about two years ago using a puller borrowed from my MB tech brother in law. It was not an MB tool,however, he made it on his lathe and it fit perfect. Even with the tool it was a TOUGH pull. My brother in law said that the other techs in the shop don't use the MB tool, they ask to borrow his. If you used it you would know why it fit so well.

It is important to align the new bushings correctly or they won't last long. It's important to look at the diagram in the book and install them in that orientation.

Good luck,
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Old 02-20-2005, 09:54 PM
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Join Date: Oct 2004
Location: San Diego, Ca
Posts: 24
Hey Larry,
I did align according to the service CD. I was questioning the actual design. I think the rubber should be solid around the aluminum internal bushing. Just an observation, but keep in mind I'm not an engineer.

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Old 04-25-2007, 08:48 PM
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Join Date: Sep 2006
Posts: 40
Could someone tell me how to use the makeshif tool? Do I have to use my hand to push/pull the rod? Or Do I turn the rod and gradually push/pull the bushing out/in? I am little confused how Dennis sets it up? Thanks.

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Old 04-25-2007, 09:04 PM
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Join Date: Jul 2003
Location: Montreal, Quebec
Posts: 508
Congrats. for having had the courage to tackle this job.

My bushings were also shot and I needed to replace them. I looked at the general area for about half an hour before deciding to have it done at my favorite benz specialist (not a dealer)

1 hour and a half later, the job was done. Total cost $150. The guy surely deserved his money.
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Old 04-30-2007, 05:27 PM
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Join Date: Aug 2001
Location: USA
Posts: 7,988
Make sure you read the service manual closely before attempting this. The bushings do not just get pulled into place until you think they're seated properly. The factory tool includes a precision measuring device, and the right-side bushing is to be pulled into place so that it's a certain distance from the front diff mount hole in the subframe. The left bushing is installed to where the thrust piece contacts the subframe (again, with the OE tool.)

I'm about to attempt this myself (with the $115 tool from Performance Products - can't afford $500 for the real tool) and I'm going to measure where the old ones are, and install the new ones to the same position. If you don't get them in the proper place, the bushings will be under strain, most likey causing premature failure.

Here's a link to the factory procedure:

And, here's a post with very good, detailed instructions:
Got the w124 300d Diff mount repaired!

Dave M.
Boise, ID

1997 E420 - 155kmi (Bugeyes)
1994 E420 - 145kmi (Blondie)
1993 500E - 193kmi (Lollipop)
1992 400E - 189kmi (Stinky Dirty)
Check out my website photos, documents, and movies!

Last edited by gsxr; 04-30-2007 at 05:38 PM.
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