Transmission mounts bad?

87 Pete

May 25, 2001
How do you check them?

Are they tough to replace?

Use GM mounts or any brand?

The reason I suspect them, is recently I'm getting ridiculous amounts of knock retard, between 4k-5k rpm. I have way adequate octane (110), I've also replaced motor mounts, I have a tie-down, and the DP isn't hitting.

I've also noticed an "odd noise" when putting the car in reverse, very subtle, but it didn't feel right. FWIW, the car has 90k miles, and I guess the mounts are original. TIA.
It is not too hard too get the mount out at the tail of the tranny. Mine is out currently and waiting for one to arrive in the mail. The GM part for the tranny mount is not available any more... checked last week. I have a little clunking going on when I put the car in reverse also and the old mount looked a little beat up so I am hoping that replacing it will "tighten" things up I bit... I will let you know how it turns out.


What about Poly?

anyone ever use a poly mount? I don't think I have any problems but I notice that when it shifts hard there seems to be some spring in something. I wonder if a poly mount would tighten things up.

Even after you change the mount, if anybody has taken out the body rubber grommets between crossmember and frame rail, has proven to give a knock on shift but not excessive and only at shift. In order to use poly mount you need a Monte SS crossmember and one of three choices are available.
You redesign and fabricate your crossmember to accept the gm poly mount keeping your body "grommets " in place
You get a monte ss crossmember and then grind out the mount holes to use your Body gromments and you dont have to play with mount location.
You use monte ss crossmember , energy suspension poly mount and bolt that sucker to the frame. This is the most rigid and keeps moving around to a minimum, however you may get knock on shift, and feel more "road vibration" then before..

These are the best upgrades.
Thanks Bruce

Good info. I guess I should reconsider a poly mount if it is going to increase knock. the 87 Olds Cutlass 442 crossmember the same as the monte??? One of those is just down the street in a yard.

Paul Ferry - HR Parts-N-Stuff had some bolt-in Poly mounts at Bristol. Give him a call.
Are these rubber grommets still available from GM that go between the fram and crossmember? When I installed my 2004R I never noticed any... I have a clunk about half of the time when I put it in gear, this occured both before and after the tranny swap. I thought it might be the U-joints but they seem fine. Could this be the problem? and possible the tranny mount also?

Montes didnt have it (the body grommets) . Just Gn or turbo buicks.