The transmission mount bushings on the E36 like the BMW 325i are rubber, and like most things rubber, they tend to wear. Rubber is used in cars to reduce vibrations, and after many years and many miles the rubber tends to break down and deteriorate. While driving a stock BMW, it's possible to see the gearstick move about while driving in 3rd of 4th gear. This inherent play can lead to an expensive and catastrophic mis-shift (4th-3rd when trying to go 4th-5th). I almost made that mistake myself before I replaced the transmission bushings to a slightly firmer polyurethane bushing. But for those that are just replacing because of wear, OE rubber bushings will be great for normal use, and keep vibrations and sound minimized inside the vehicle. This is a very simple DIY that almost anyone can do.
Tools
- 3/8th drive socket set 10-14mm sockets
- 10-14mm wrenches
- New bushings and new hardware
- Safety Glasses
- Gloves
To start, securely get the car onto all four jack stands and support the transmission with a floor jack. Having the car securely on jackstands is very important; A floor jack is not enough, they can slowly lower or fail and you do not want the weight of a car on you. Always use jackstands in secure locations.
Use a 13mm socket for the bottom of each mount, with an open 12mm wrench on top. Once the mounts are loose it’s quite simple to slide the old out and put the new in and re-tighten in same fashion as removing it. Now you are free to lower the car and enjoy the new mounts.
If needed you can slightly raise the transmission once the mounts are loose to make putting the new ones in easier.
Rubber vs. Polyurethane
The material you choose is really dependent on what type of driving you do with your car. If it is just your daily driver or one that is basically stock, OE bushings are the best way to go for comfort and noise reduction. For those that are a little bit more likely to enjoy spirited driving, consider a polyurethane bushing. There are several performance-oriented bushings on the market, but I used the “blue isolated” poly bushing from UUC Motorwerks. It is not a bolt-through style bushing which is what a dedicated track car would require. Too stiff of a bushing can cause a dramatic increase in vibration. Remember, most bushings are rubber for a reason. I immediately noticed a difference when I drove the car after the firmer bushings were in place. But like clutches, there is such a thing as too stiff, and it is possible to buy stiffer than you need.
