vibrations at speed with poly trans mount
vibrations at speed with poly trans mount I just installed my prothane trans mount, and since then ive been getting vibrations at speed 60+mph. Is it possible that the prothane mount is taller than the stocker and thats throwing the pinion angle off causing vibrations? My car was smooth as glass before i installed this. I already sold my trans mount so i cant measure it myself...any input? Anyone have one lying around that they could measure? If the prothane is taller im going to shave mine down.
Thats possible. But the prothane is a hell of a lot stiffer than the stocker, so it wont absorb the vibrations that the stock unit would normally absorb. I had a prothane trans mount installed on my car at one point. Vibrations drove me nuts so i put the stock unit back in. Cleaned up alot of the vibrations. I have heard that the energy suspension mount is kind of the middle of the ground poly mount. Between the stock mount and the prothane as far as stiffness goes.
yeah i knew the mount was going to cause vibrations, but this is more of a speed vibration sort of thing. Im fine with the stiffness vibrations, but the speed vibes you can feel through the steering wheel....it almost feels like my wheels are out of balance....thats really the best way i could explain it.
Teching In
Joined: Oct 2008
Posts: 27
Likes: 0
From: Oklahoma
Ive read from many sources that running poly trans with stock rubber motor mounts is a bad idea... some people who run just poly trans have no problem but i seem to think this is b/c there motor mounts are not shot/worn- usually you find shot motor mounts in cammed cars (more aggressive vibes are introduced to mounts on motor). i recommend you check your motors mounts that may be the reason the poly trans are not working for you like they have others. If you still want a measurement of the stock trans mount let me know ill get em on here by tonight. And as far as "the speed thing" it prolly has to do with you drive shaft spinning at crazy angles while your eng vibe its transfered to the transmission mounts instead of the eng mounts.
Last edited by donwood84; May 3, 2010 at 04:51 PM.
Ive read from many sources that running poly trans with stock rubber motor mounts is a bad idea... some people who run just poly trans have no problem but i seem to think this is b/c there motor mounts are not shot/worn- usually you find shot motor mounts in cammed cars (more aggressive vibes are introduced to mounts on motor). i recommend you check your motors mounts that may be the reason the poly trans are not working for you like they have others. If you still want a measurement of the stock trans mount let me know ill get em on here by tonight. And as far as "the speed thing" it prolly has to do with you drive shaft spinning at crazy angles while your eng vibe its transfered to the transmission mounts instead of the eng mounts.
well it turns out that the mount that i ordered is not the correct mount....if donwood or anyone else could give me a measurement on the stocker it would be greatly appreciated. Thanks!
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you running the "preload plate". is your car lowerd, are you running a adj TA with some - pinion angle. do you have a diffrent Trans Xmemeber.........
try removing the plate, you can get a vibration at speed from to much driveline angle. SOme guys had to shim there trans Xmember down with 1-2 washers even. Some bolt on parts don;t play well.
try removing the plate, you can get a vibration at speed from to much driveline angle. SOme guys had to shim there trans Xmember down with 1-2 washers even. Some bolt on parts don;t play well.
you running the "preload plate". is your car lowerd, are you running a adj TA with some - pinion angle. do you have a diffrent Trans Xmemeber.........
try removing the plate, you can get a vibration at speed from to much driveline angle. SOme guys had to shim there trans Xmember down with 1-2 washers even. Some bolt on parts don;t play well.
try removing the plate, you can get a vibration at speed from to much driveline angle. SOme guys had to shim there trans Xmember down with 1-2 washers even. Some bolt on parts don;t play well.
Teching In
Joined: Apr 2010
Posts: 8
Likes: 0
From: Atlanta, GA Orlando, FL
Was at Summit Racing the other week talking with some guys there, had looked at getting that mount. Until they said almost all aftermarket ones are about an inch taller than the stock mount, and would throw the pinion angle off, to stay with a stock replacement. Dunno if its true but maybe check ur pinion angle and see if its thrown off..?
Thanks for the reply blacked out...yeah my pa is definitely off because of the mount...I just need someone to measure their stocker for me so i know how kuch I have to shim it
Staging Lane
Joined: Jan 2010
Posts: 62
Likes: 0
From: Ankeny,iowa
Im having the same thing happening to my car, rode smooth until installing the poly mount, i even took out the plate and filed the hump on top of poly mount down which allot recomend. My original one came apart so i don't have it anymore. I am going to go back to the original mount. I checked many parts stores and the original mount for the 98+ has to be purchased through GM. Im looking for a nice used one as well if someone is selling theirs, i will trade my Poly one if you want it, only been driven with for 3 weeks!
Ill try to get by the shop and get it up on the lift and see if i can measure how tall the stock is.. 
i have installed several poly mounts into f-bodies and every time there is a vibration issue due to the poly mount being taller. easiest way to fix this is to shim the trans crossmember lower to compensate for the increased height of the poly mount.
i use 3/8"x2" steel betweem the crossmember and the body. you have to cut each side to length and drill the holes for the mounts, but it will stop the vibration. washers can be used too but i like the fact that if you use 3/8x2 steel it contacts the entire mounting surface against the floor of the car.
taking out the preload plate really didn't make a difference in any of the installs i did. also adding poly motor mounts doesn't make a difference in stopping the vibration either. hope this helps, it did for me
i use 3/8"x2" steel betweem the crossmember and the body. you have to cut each side to length and drill the holes for the mounts, but it will stop the vibration. washers can be used too but i like the fact that if you use 3/8x2 steel it contacts the entire mounting surface against the floor of the car.
taking out the preload plate really didn't make a difference in any of the installs i did. also adding poly motor mounts doesn't make a difference in stopping the vibration either. hope this helps, it did for me
i have installed several poly mounts into f-bodies and every time there is a vibration issue due to the poly mount being taller. easiest way to fix this is to shim the trans crossmember lower to compensate for the increased height of the poly mount.
i use 3/8"x2" steel betweem the crossmember and the body. you have to cut each side to length and drill the holes for the mounts, but it will stop the vibration. washers can be used too but i like the fact that if you use 3/8x2 steel it contacts the entire mounting surface against the floor of the car.
taking out the preload plate really didn't make a difference in any of the installs i did. also adding poly motor mounts doesn't make a difference in stopping the vibration either. hope this helps, it did for me
i use 3/8"x2" steel betweem the crossmember and the body. you have to cut each side to length and drill the holes for the mounts, but it will stop the vibration. washers can be used too but i like the fact that if you use 3/8x2 steel it contacts the entire mounting surface against the floor of the car.
taking out the preload plate really didn't make a difference in any of the installs i did. also adding poly motor mounts doesn't make a difference in stopping the vibration either. hope this helps, it did for me
