I installed a new Polyurethane Trans mount on my 68 camaro when I put everything back together and it is roughly 3/8" to 1/2" taller then the factory mount. TH350. Now I have about 475hp/500lb torque on this motor and didnt think a stock mount would hold. I am having some noises coming from the tranny like a thumping or light knocking noise. I checked all the bolts on the converter and the flexplate and they are tight. My only other thing I can think of is the driveline angle with the new mount. Maybe the tranny is hitting the tunnel on top of the tranny and reverberating through the car. I went to Napa and bought one of there trans mounts which is a piece of %$#@! This thing doesnt seem like it could hold 100lbs of torque. Where can I get a good one that is stock height? I believe the original one would work but I threw mine away. Anybody have any suggestions or maybe a mount they could sell? Napa had teo they tried to sell me, one had a treaded rod coming out of it and the other one was the correct one only not real beefy at all.


Thanks, Erik

I have the poly mount as well as the driveshaft loop that mounts under the tranny mount with no issues. Perhaps the solid mount is transmitting noises that were they're previously? I wouldn't expect the angle to change all that much unless it was too much to begin with. Mine is now 2.5*.

I have a similar issue with a poly mount. And I too looked at the made in India NAPA mount. That was junk.
I have a sometimes noise when shifting from reverse to drive. The mount I have does sit a little bit higher than a stock mount but I didn't think there was enough increase to be a problem. My noise sounds like the crossmember is loose but it isn't that. The transmission does not sit high enough to be hitting the tunnel. I can only attribute the noise to the mount change. I don't have any vibration like driveshaft angle would cause or any other issues even under hard accelleration.

First off, as far as I know there is no direct correlation between how much hp/torque a motor produces, to how large/strong the transmission mount has to be. So if you believe that you have to have a stronger beefier mount because your engine is putting out more power-don't worry about that any more because it just is not the case.

The transmission mount has weight on it 90% of the time.. so it does not have to be very stout or strong. It essentially acts as a cushion for the weight of the transmission, and to a VERY SMALL degree, some of the engine weight. Looking at any of the mounts that you have now, or have seen, what is the likelyhood that the weight of your engine and transmisison could crush them? Not very likely right? That is all you need to be worried about.

That cushion/mount on the back of the tranny is designed to have a little bit of movement to it so that as the motor rocks over on the engine mounts under high torque conditions, the tranny can also "roll" just a little bit with it.

If your trans. mount puts the rear of the engine/transmission at the correct angle (in relation to driveline angle) then you are set..

Here is my personal experience with the poly mount:

http://www.camaros.net/forums/showthread.php?t=52662&page=2&pp=15&highlight=poly+mount

It is easy enough to swap the rubber one back in and see if your issues go away.

The poly trans mount has a 1/4 thick metal plate that must be installed (not sure why). Did you install that plate? If you remove the plate is your driveline angle imporved. Are you measuring the driveline angle while the car is at ride height or on jackstands? And finally are you sure your drive shaft yoke is not bottoming out on the back of the trans.

I havent really measured the driveline angle at all. Everything is stock except for the trans mount. I really dont think the mount will cause the noise to go away but I figured I would check just to make sure. And Yes, I do believe that the mount does help in high torque applications. I know somebody ho snapped one on the line when he launched.

Anyways, what are the possilbilities of a cracked flexplate or something making the noise? I checked it out and it seems fine but I guess it could be a hair line crack or soimething.

Thanks, Erik