Homebrew Poly Diff Mount

Differential mounts in E24's and E28's are a joke. The metal started cracking in a new mount in six months. The first replacement mount I bought was substantially beefier than the original mount and still only lasted six months. I'm guessing the stock non-M mount is superceeded by the M5 mount, which means I'm routinely destroying the best mount available.

I decided to reinforce a diff mount with polyurethane at the same time as a pair of subframe mounts. I have an on;line source for two part liquid polyurethane on the subframe mount page. The result was a very siff solid mount which I haven't managed to destroy after seven months (as of 12/99).

Still all in one pice as 0f 6/2/00. Ed


Here is a post from the M535i Digest about the poly diff mount:


From: Robert Snyder

Date: Sat Jun 3 2000, 6:39 AM GMT-05:00

To: BMW M535i Mailing List

Subject: Re: [M535i-List] Flexane upgrades, ......BMW M535i Mailing List - http://M535i.web.com

I have flexaned my rear diff mount with Flexane 80. It solved the problem of
ripping out but is a little noisier now. Also have K-mac rear trailing arm
bushings. The instructions are bad as for installation and the old bushings
have to be carefully cut out. They will not press out. I have had one of the
eccentrics slip so I recommend marking or tack welding bolt head inplace.
Some alignment shops don't have a clue as to how to adjust them.
Feel free to dress up this info how ever you want.
88 535is



Here is the stock "upgraded" diff mount (M5 mount?)



Another angle. Look at all the open space. The original mount in my car did not have the two "ears" at the top left and right corners of the mount in the picture. Is this the M5 mount I've heard so much about? The instructions for the polyurethane say that rubber parts should be primed with a special Devcon primer. I guessed that the primer is just a solvent that allows the poly to bond to clean surfaces, so I cleaned my parts with acetone. The acetone took off a lot of the gray paint on the diff mount.


The mount taped and full of polyurethane



Another shot. The socket head cap screw is there to keep the liquid poly from running down into the hole that the diff mount bolt screws into.



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