Inverted 930 trans mount
- Thread starter kaspa
- Start date
Terry Oxandale
Skinny Man
I did the same thing with aluminum, and like you, not getting full engagement of the threads. So far, so good though.
I don't like the idea of hanging the trans on a mount that's built to take pretty small compression loads. Because the engine-transmission "system" creates the torque that drives the wheels, the forces can get quite high.
The torque reaction should be handled by the motor mounts and/or block plate.
What some here are trying to do is to give more support to the weight of the transaxle. At least that's what I was trying to accomplish rather than merely relying on 4 - 8mm studs (from memory) that bolt the transaxle to the block adaptor.
Here's my solution along with a template for the G50 crowd::
competition transaxle support
Cheers..
:thumbsup:
I had support rods from the frame down to a mount at that pad when I first built my car. Then later I removed them. I had the engine solid mounted at the sides and mid plate. Seven years of 20-25 days each year of track use and never had an issue.
Terry Oxandale
Skinny Man
Yes. I have solid mounts on the engine, adapter plate, and the rear support for the transaxle (five points). Tighten the front two, and back support, then tighten the two middle support (adapter plate) bolts last (floating until tightened), ensuring no pre-stress on the transaxle. Like Dave said, no issues yet, but life is still young.
Solidly mounting the engine and trans at the original engine mounts and at the bell-housing interface will take all the torque stress nicely (at the expense of vibration). Unless there's something extra in the OP's setup, I'm sticking with my recommendation.
Bob, even with solid mounts and no rear trans mount, no vibration whatsoever. I mean the car was a full race car with solid rod end suspension, so it felt smoother than expected.
This car will be a road car Hence the need for isolation mounts, and the mount is in its natural compression state, the engine and trans will not have any torque loads on it apart from rotational inertia, thats what your suspension arms do, the mounts therefore are just for support.
the pic shows the trans upside down so i could get a detailed photo, the mount is under the trans when fitted.
kaspa
I stand corrected on that point. I assumed that the picture was right-side up.
That is not how it works. The driving torque reaction must be absorbed somewhere, and in this case it's through the engine/transmission mounts.
Terry Oxandale
Skinny Man
I would agree. As much or more of an issue is chassis rigidity. In a perfect frame, the solid 5 or 6 point mounting is of no consequence because the engine/adapter plate combo (4-pt) should eliminate detrimental torque on the transaxle case. Unfortunately, any flex in the frame behind the last rigid engine/adapter plate mount, will be imparted onto the case. For my situation, the sway-bar/suspension forces are all within close proximity to the adapter plate location with additional tubing (triangulation) in that specific area, thus the framing extending behind this area for the transaxle support is exposed to very little dynamic suspension/twisting force.
My guess is that the engine mounts on John's project are more rigid (thinner bushings more widely spaced apart) than the transaxle mount, which would not allow the transaxle case to become the limiting element in this torque transfer, and the 3-point aspect of his mounting mitigates frame flex from being the issue that I had to consider.
My guess is that the engine mounts on John's project are more rigid (thinner bushings more widely spaced apart) than the transaxle mount, which would not allow the transaxle case to become the limiting element in this torque transfer, and the 3-point aspect of his mounting mitigates frame flex from being the issue that I had to consider.
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