Wipperman

My current gearbox mounts are to soft.
Im having a 944S2 with LEDA suspension (without torsion bars) and driving on Michelin cup (R-tires).
The setup generates G-forces during race and the gearbox is moving.
I bought mounts from Lindsey racing but are not sure to install them.
My question is what I will gain/lose with solid mounts.
Friends are telling me that it will create way to much force on driveshaft and put a lot of stress into the car.
Experiences?
Advice?

All the best

Anders

APKhaos

THose that have gone this route report that the major downside to solid mounts is that they set up high levels of vibration that literally cause bolts to back out all over the car!

The alternative to hard mounts is to 'pot' the stock mount with 80 hardness Urethane. This creates a fixed mount with enough give and vibration damping to avoid the problems of solid mounts. On my car, it completely solved the problem of the trans moving laterally under high G loads.

Here's a pic of my mount after the urethane treatment. Its been tested in heavy combat over more than a full season of racing.

r1moto

Tony, could you please explain in more detail the "pot" process, it sounds like an interesting idea.

APKhaos

Its simple. The material is Urethane 80, from McMaster Carr. There are various hardnesses, but 80 is what you want for this job.

- support the rear of the car on jackstands - the right rear wheel is coming off.
- Support the transmission on a stand, having lifted it slightly with a jack to relieve load on the mounts.
- remove the right rear wheel.
- remove the mount bolts, remove the fuel filter bracket.
- remove the transmission mount crossmember [two bolts, one each side]
- withdraw the crossmember through the right wheelwell. I had to disconnect the right lower shock bolt to drop the trailing arm enough to get the crossmember out, but I have 800# springs in the rear. Softer or stock rear suspension will droop enough to clear it.
- Clean the crossmember and the trans mount carefully. Lots of degreaser [Simple Green works] and lots of rinses. You want a clean surface. Dry it well.
- Find some resonably thick plastic to make a dam either side of the trans mount. I used a large laundry detergent container as a source. Look at the pic above and you will see where the dam walls were. Tape the dam walls down carefully with race tape or similar. The tape goes on the outside only - not inside the dammed area containing the trans mount. It needs to be sealed against leaks.
- Set the crossmember on a bench or floor, and brace it level. Check that it is level in both axes - you don't want to discover it is not level once you start pouring urethane.
- Slowly pour the urethane until the entire section around the trans mount is filled to the top.
- When its dry [24 hours is good] remove the dam walls, clean up any excess, and reinstall.

Nice easy job, and it makes a real difference. GOod luck with it.

r1moto

Thanks for all the info. Its a great idea. I will do it for sure. Thanks again.

The DareDevil

When you install a solid gearbox mount, do you also need to install solid motor mounts to prevent the engine from twisting the drive train?

APKhaos

No. Solid engine mounts cause a much more serious vibration problem than the solid trans mounts. The semi-solid modified stock mount avoids this problem [based on almost two seasons of race use] AND prevents the trans from swinging under high cornering loads. I run with stock motor mounts.