So my firend is talking to me today as I am helping him install a shift kit. Anyways, he was telling me how he keeps breaking transmission mounts. He replaced the front motor mounts after he went through 3 tranny mounts, and is still breaking tranny mounts. He does not have any engine work done to his engine other than a Dynomax cat-back exhaust, and has stock wheels with not that great of tires. He is not that hard on his car. It is a 1990 with the 350 TPI and an automatic, and 3.23 or so Posi rear end with the rear disks.
Any ideas?

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It's all about having fun before you knock up a chick and have to sell the car and settle down and buy a station wagon.

Cars....
1988 VW GTI 16V "The Honda Beater"
1983 Camaro/350/T-10 "Gone but not forgotten"
1985 Mazda RX-7/350/T5 In Progress "Like 10 pounds of rocks in a 5 pound bucket."

 

Never fails.

Factory trans mounts SUCK. Period. They're made of rubber with no structure to take the torque except rubber. Rubber tears. I use a Polyurethane transmission mount. Firmer than stock, soft enough to absorb vibration (too bad I can't say the same for the motor mounts), and has a design that has actual metal to absorb the torque...the poly is nothing but a damper...after 3 mounts, the poly mount would have paid for itself, for $25. May want to change the torque arm bushing while you're at it. Another $25, but more involved (requires minor grinding/drilling). Relly makes a difference, Summit and other speedplaces have them. Don't try looking at a parts store, you'll never find them. Good luck

 

DH covered it -- but I just thought you'd want to know that I'll backup his assessment

I've got a fairly stock 305 in my T/A - so no big power - but I drive it hard. I ate up at least 3 stock tranny mounts in a summer. I finally switched to a polyurethane mount about 2 years ago and I haven't touched it since.

 

These cars have the worst possible design in that area, period. The torque required to hold the rear end housing from rotating is applied directly to that mount, which attempts to tear it in half; like was said earlier, it's just a blob of spooge with no reinforcement.

With the stock L69, I could put a new mount in, and break it before I had gone one block. Everybody with one of these cars has the same problem you do.

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"So many Mustangs, so little time..."
ICON Motorsports

 

The guys are right the stock tranny mounts suck big time. I broke 2 in one day. I then put in a polyurethane mount. I haven't had a problem since.

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Jamie James
1986 Iroc-Z 305 TPI
1.90 60 ft 14.15@ 95.75
1.74 60 ft 12.84@107.75 on the bottle.
My IROC:
http://personal.nbnet.nb.ca/jjames/homepage.htm

 

Thanks a lot folks....

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It's all about having fun before you knock up a chick and have to sell the car and settle down and buy a station wagon.

Cars....
1988 VW GTI 16V "The Honda Beater"
1983 Camaro/350/T-10 "Gone but not forgotten"
1985 Mazda RX-7/350/T5 In Progress "Like 10 pounds of rocks in a 5 pound bucket."

 

Guys, I have an 86 TA with a bunch of modes to motor and trany and I have been through too many stock mounts to count so I switched to poly and have been through several of them also. Finally got an all metal mount from Speed unlimited. Now I have stripped the bolts right out of the trany. Whats next?? any suggestions??