Hi folks,

So earlier today I broke my transmission mount for the third time in 6 months. Amazingly despite flopping around like a fish, there's no cracks or leaks. Obviously though, it's time to find the cause before I DO do serious damage.

Talked to a buddy of mine who is really knowledgeable, he thinks it's worn motor mounts (and they are pretty bad) letting the motor and tranny twist too much. Which makes sense to me so I'm going to change the mounts. Chilton makes it sound easy so I'm wanting to do it myself and figuring I'll go to poly mounts. Pictures of the polies look pretty different from the stock stuff though.

My question is, how difficult would these poly mounts be to put in compared to stock replacements?

Prothane Motion Control 7-1909-BL - Prothane Motor and Transmission Mount Kits - Overview - SummitRacing.com

Do they need any drilling or cutting or do they just bolt right in?

Finally, any other ideas why the hell I would keep breaking my trans mount? What else should I check while I'm underneath it?

Thanks!

 

The mounts are a clam shell style with the rubber isolator in a steel body that the factory rivets together. You have to drill the rivets out to open them up and the poly mounts go in place of the factory rubber mounts. Good drill bits, drill motor, punch/hammer to get them out after you drill the rivets is all you need. There is a correct orientation to the metal tabs on the mount (safety stops) relative to the shell so take a picture of the old ones before you take them apart.
I think if it was ujoint/driveshaft that was tearing the mount up, the vibration would be noticeable.

 

I do have vibrations. The guy that installed the mount said it concerned him, but that his "Engine guy" looked it over and said it wasn't anything to worry about. A different shop said it was a condition of "An old car with a big engine" and not to worry about it.

U-joints are pretty cheap and not too difficult(I've done them on my truck), so if you think it could be a cause, I should probably change it out too. 15 years and 125k on the clock, the car has a lot of worn things needing changing anyways.

 

What have you been replacing the trans mount with? Stock replacements from the parts store? If so, I shredded 3 of 'em in a week in my A4 94 after doing headers about 10 years ago, and on my 95 M6, the stocker was torn when I bought it. Since it's stock, I put the parts store one on there. Shredded 2 in 3 days a week ago. I could identify the exact moment it happened each time, in both cars. HEAVY ACCELERATION from a stop.

The solution in both cases was a polyurethane trans mount. I've used an Energy Suspension unit in both cases. The one in my 94 A4 still looks new after 80k miles, and would still be racking up miles if I hadn't smacked a guardrail after deciding to drive with a 103 degree fever.

The one in the M6 has survived it's first 3 days admirably.

Personally, I doubt your motor mounts are the problem in this case.

 

I don't think a stock mount will be failing that regularly given the mods on OP motor; something else is wrong. If he feels vibration could be drive shaft, u joint, even internal tranny, or motor mounts. Yes a poly is much tougher but that is not solving the problem of the OP, only hiding it.

 

I do have a few other mods, but I'm not putting out much, if any, more than a stock machine. Also I haven't launched it very hard since the first mount.

The previous mounts were all stock napa/autozone replacements installed by a shop. I'll be doing this one myself and already planning to use a poly mount, so that'll be taken care of.

I've got my truck happy for the nonce, so I'm going to do a lot of maintenance on the Camaro. Starting this week it's going under the knife for new control arm bushings, ball joints, spark plugs, wires, fuel pump, motor mounts, trans mount and U-joints. If I still have vibrations, I'll look into the driveshaft and other causes then.

I'm still open to any advice. Thanks folks!

 

I broke a couple of stock ones after the install of the first cam, I then went with a poly and it caused too much in cabin noise and vibration for my tastes.
I think what I ended up with was the 1LE trans mount??? It was on certain 3rd gens and is a solid rubber mount compared to the hollow center stocker, it's lasted 4-5 years and 35k miles.
As far as motor mounts, I used a poly only on the driver side due to vibration also and putting on driver side only prevents motor from torquing over any and causing the headers to hit something.