Author Topic: Replacing Rear Axle Differential Mount  (Read 3185 times)

Mike K

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Replacing Rear Axle Differential Mount
« on: October 15, 2016, 17:50:28 »
Having replaced the shocks, compensating spring, 4x suspension springs & rubbers, I was still not entirely satisfied with the ride of the car over bumps and on rough roads, it still felt slightly hard.

So this afternoon I tackled a job that I've been wanting to do for a while, and replaced the Rear Axle Differential Mount.
I followed the procedure detailed here in Sept. 2003, it was extremely helpful - so indicative of what a great resource the Pagoda SL Group is!
http://www.sl113.org/forums/index.php?topic=806.msg3842#msg3842

When I lifted the plastic box cover in the boot/trunk it was immediately obvious that the mount was shot, see:
Pic #1: The rubber in the mount has completely collapsed & worn; metal on metal with no rubber buffer left.
Compare to:
Pic #3: New mount with unworn solid rubber.

I did this job on my own, even though it's probably a 2 person job. The whole process took me about 45 minutes from start to finish.

You need 2 jack stands, a trolley jack, a 17mm socket spanner for the 4 mount bolts & a 24mm socket spanner for the centre plate bolt & 2 pry bars or large flat screw drivers.

My advice to anyone doing this is to first loosen the bolts prior to lifting the car up.
 
Once the car is jacked up from the differential, place the jack stands under trailing arms.
Leave the jack in place so that you can manipulate the differential up and down as well as laterally, when fitting the mount.
 
As you jack the car up from the differential, the mount is raised into the boot/trunk.
Loosen and remove all the bolts completely, starting with the 4 mount bolts and lastly the centre plate bolt.
Then pry the old mount out, I used 2 pry bars.

The tricky part is centering the arm that comes up from the differential through the mount cavity into the boot/trunk.
Once you place the new mount over the arm you have to then lower it so that it fits squarely back into the mount cavity.
I did this by raising and lowering the jack and moving it from side to side.
You can see the the arm centering or decentering in the mount cavity as you move the jack around. Plenty of patience required with this!

Once the arm was centred, I placed the mount over it, fitted the centre plate over the mount & bolted it onto the arm, in order to hold the mount in place.

I then lowered and manouvered the jack laterally so that the mount dropped squarely back into its cavity. It took 5 or 6 attempts & the use of a variety of many vulgar words to centre the arm and drop the mount squarely back into the cavity. This is the most tricky part.

Once the mount has been lowered back into place, you can then insert the 4 mount bolts and hand tighten with the spanner.
Final tightening of all 5 bolts should only be done once the car is resting on the ground on its own weight with stands and jack removed.

The difference in handing and ride is astounding!

Next week I'm tackling the trailing arm rubbers.

Best,

Mike
« Last Edit: October 15, 2016, 21:40:07 by Mike K »
Feb. 1971 Mercedes 280SL Auto  LHD (Last of W113 Series)
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ja17

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Re: Replacing Rear Axle Differential Mount
« Reply #1 on: October 16, 2016, 05:18:22 »
There is a factory special tool. It is a cone which centers-up the vertical arm so it can easily be raised up and centered through the new mount. 
Joe Alexander
Blacklick, Ohio
1969 Dark Olive 280SL
2002 ML55 AMG (tow vehicle)
2002 SLK32 AMG (350 hp)
1982 300TD Wagon turbo 4spd.
1963 404 Mercedes Unimog (Swedish Army)
1989 flu419 Mercedes Unimog (US Army)
1998 E430
1974 450SLC Rally
1965 220SE Finback