Polyurethane Engine and Transmission Mounts

Summary

Replace aging, weakened original BMW engine and transmission mounts with race grade polyurethane mounts.

Start Date: September 1, 2012

Odometer: ~310, 000 km

Total cost: USD$201.98 + Duties and brokerage

My original BMW M50 engine mounts were showing signs of failure: torn at the bolts and cracked rubber throughout. Failed engine mounts in a performance car (particularly one with a very tight fit motor swap) can cause damage to other components such as hoses (pinching), propeller shaft (aka driveshaft), flex disc, radiator, electric radiator fan, and belt-driven accessories such as the water pump (if the motor shifts forward under braking). Motor movement on the track can also cause handling instability and sudden weight shifting. Considering the stress track driving puts on the drivetrain, my mounts needed replacement.

Parts

Journal

Initially I intended to simply replace the old mounts with new standard BMW mounts, but I discovered stiffer mounts for track use available from several suppliers. Without knowing exactly what to expect, I ordered Polyurethane Motor Mounts from Revshift, who make a specific mount for M50 swapped motors in E30s.

Polyurethane M50 Motor Mounts for E30

To keep the entire drivetrain secure, stiff motor mounts are best paired with similar grade transmission mounts, so I ordered matching transmission mounts.

My transmission is an E36 Getrag 250, which is a direct fit swap for the Getrag 240 that was originally on the car, so the Revshift polyurethane E30 mounts fit properly. Both the engine and the transmission mounts were tricky to fit perfectly, but with some perseverance did eventually go on. It took more work to get things right than a stock replacement.

Here's one of the engine mounts installed:

Here are the transmission mounts installed:

The new mounts are fantastic. I was not expecting such a dramatic change to the car. The entire feel is tighter and more responsive. Very much worth the effort, and a great upgrade to the car's predictability and connection to the road on the track. However, a note for street-driven car owners: these are not recommended for daily driving as the seriously affect ride comfort. The race-grade (95a) mounts bring all the vibration of the engine and transmission into the cockpit, creating a rattling that you can feel throughout the car, in your seat and in the steering wheel, especially at slow speeds. At higher speed on the track, however, the car feels smooth and cleanly planted on the road. Highly recommended for track use.