Project E36 M3 - Sagging Transmission Liner Meets Clever Solution October 29 2013

A common problem on BMW E36 chassis cars is that the transmission tunnel liner starts to sag over time. We noticed ours sagging against the drive shaft to a point where it had worn the paint off. Some people elect to cut out the liner where it is sagging. We didn't want to slice and dice our liner if we didn't have to. It keeps heat and noise out of the cabin, and it protects the chassis from abrasions and corrosion.

We were in the middle of a guibo and drive shaft center support bearing replacement job, so it was the perfect time to tackle this.

We had some neodymium magnets that we would use to reattach the liner to the transmission tunnel. They came with countersink holes in them already, which made installation a breeze. Here you can see a mock-up of the setup. The countersink screw goes through the magnet, liner, washer and nut in that order.

But first, a word of caution. Neodymium magnets are so incredibly strong that if they get too close to each other, they can snap together with enough force to crack. 

Working on a different project using these magnets, my hand got in the way and got pinched hard enough to get a blood blister. It is far from being a serious injury, but if you are using bigger magnets or wear nipple rings, it could ruin your day.

I drilled a hole in the liner, using a piece of wood to back it. I chose a location where the magnet would have a good flat area of the transmission tunnel to stick to. I then very carefully fastened the magnet to the liner with the screw, washer and nut. Keep the magnet as far away as you can from the chassis until you are ready to stick the magnet to the car. I chose stainless steel hardware because this area will be exposed to corrosion inducing moisture, but also because stainless steel is not ferromagnetic and won't stick to the magnet. It would be difficult and dangerous to try to put everything together with the magnet fighting you the whole way.

Here is the finished product. The liner is tucked well out of the way. If I were to do it again, I'd add two more magnets just to be extra secure. I'm not worried about the magnets moving. They have about 30 pounds of pulling force each. I'm more concerned about the liner sagging in areas away from the magnet.

The paint on the drive shaft was worn down, so we sanded it, degreased it, primed it, painted it and re-installed it. Everything is close to being back in the factory condition. Like avoiding any sort of amputation, we avoid slicing and dicing on our street cars. I know it is just a silly liner, and I know some would not hesitate to cut it out, but not me. For those that cringe at cutting out the liner this magnet trick is not a bad alternative.

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