View Full Version : Solid transmission mount
Quiny
09-17-2014, 08:20 PM
Has anyone considered modifying the stock tranny mount and making it solid. I was looking at the old one that I replaced and it looks like you could cut out the rubber and weld a heavy piece of flat stock across the open end, then just drill the flat stock for the frame holes. My reasoning is that first it will stiffen up the engine which has been said to be a problem and it would lower the transmission in the rear by about 3/8" which would allow the engine to sit more level. I may try to fabricate it this weekend, anyone see a downside?
Aero STI
09-17-2014, 08:44 PM
I made my motor mounts solid by welding plates on them, the trans mount was next. I don't see any issue and I like the idea of dropping the trans slightly to level things out.
Rasmus
09-18-2014, 12:31 AM
My thoughts:
It would be foolhardy to solid mount an aluminum cased motor and transmission by only three points (i.e. two motor mounts and the trans mount) to a steel framed chassis. There will be inherent vibrations and shocks that the powertrain see and allowing all that energy to hit all a once, time and time again, at the same three points, might crack the aluminum cases. Now, I don't actually know this. And I could be totally wrong. I'd love to be corrected if I am wrong.
If you wanted to solid mount an aluminum cased powertrain, I'd hazard you'd want to do it with aluminum motor mounting plates that deliver that energy at many places around the motor and transmission.
I would think that it would be doubly bad to solid mount the trans while the engine is mounted with 'rubber' or poly mounts. Something's really gonna want to crack if you do it that way.
The wisdom I've always read that that you should use the same durometer in all your powertrain mounts. Never mix hardnesses.
I've seen american muscle sporting front or rear motor support plates when there was a concern about too much power being resisted by only a few mounting points. Perhaps something like that could be bought or fabricated is someone is concerned.
Front 1 (http://i213.photobucket.com/albums/cc211/lukeduke406/Prostreet%20RX7/CIMG0386.jpg)
Front 2 (http://raceprovenmotors.com/images/waterjet/slides/IMG_2421.JPG)
Rear 1 (http://i.imgur.com/Vi8w8.jpg?1)
Rear 2 (http://www.candbmotorsports.com/projects/racecoupe/00000187.JPG)
Another plus about dropping the trans would be less chance of under-filling the transmission fluid, which seems to be a problem in the 818 location if people aren't careful.