Is there a write up on Swapping Tranny Mounts?
05-07-2014, 02:46 AM
#2
Okay, I just wrote this up.
Replacing your transmission mount:
First get the front up high enough so you can get under the car easily. Go ahead and loosen and remove the nut or bolt holding trans mount to the trans X-member. Now place a jack under the transmission in front of the X-member, then jack the trans up until you can just see its off the X-member. You can then put a jack stand under the trans to keep it in place while you remove all 4 trans X-member bolts and remove the X-member from car.You can now remove the 2 bolts that hold the mount to the trans and replace the old mount with a new one, then re-install the 2 bolts and tighten them down. Now you'll want to re-install the trans X-member with it's 4 bolts. Thread the bolts almost all the way in so the X-member can still be moved around if needed. Okay go ahead and slightly raise the jack and remove the jack stand, and then slowly lower the jack until the pointed end of the New Gm trans mount is through the X-member trans mount hole, then stop the jack from going any further down. Now if this was a poly mount then just lower it enough that you can see whether the trans mount bolt hole is lined up with the X-member mount hole, If it's not lined up then move the X-member around until the holes are lined up. Once they're lined up get the bolt started a couple of turns, then you can finish tightening down the 4 X-member bolts. Finally go ahead and lower the jack the rest of the way down and install the GM nut and fully tighten it down, or tighten down the bolt with the poly mount.
Don't forget to tighten all fasteners to factory torque specs.
Torque specs:
GM trans mount lower nut, 77 lb.ft.
Poly trans mount lower bolt/nut, 37 lb.ft. (grade 5), 52 lb.ft. (grade 8)
trans mount upper bolts, 36 lb.ft.
trans X-member bolts, 43lb.ft.
Replacing your transmission mount:
First get the front up high enough so you can get under the car easily. Go ahead and loosen and remove the nut or bolt holding trans mount to the trans X-member. Now place a jack under the transmission in front of the X-member, then jack the trans up until you can just see its off the X-member. You can then put a jack stand under the trans to keep it in place while you remove all 4 trans X-member bolts and remove the X-member from car.You can now remove the 2 bolts that hold the mount to the trans and replace the old mount with a new one, then re-install the 2 bolts and tighten them down. Now you'll want to re-install the trans X-member with it's 4 bolts. Thread the bolts almost all the way in so the X-member can still be moved around if needed. Okay go ahead and slightly raise the jack and remove the jack stand, and then slowly lower the jack until the pointed end of the New Gm trans mount is through the X-member trans mount hole, then stop the jack from going any further down. Now if this was a poly mount then just lower it enough that you can see whether the trans mount bolt hole is lined up with the X-member mount hole, If it's not lined up then move the X-member around until the holes are lined up. Once they're lined up get the bolt started a couple of turns, then you can finish tightening down the 4 X-member bolts. Finally go ahead and lower the jack the rest of the way down and install the GM nut and fully tighten it down, or tighten down the bolt with the poly mount.
Don't forget to tighten all fasteners to factory torque specs.
Torque specs:
GM trans mount lower nut, 77 lb.ft.
Poly trans mount lower bolt/nut, 37 lb.ft. (grade 5), 52 lb.ft. (grade 8)
trans mount upper bolts, 36 lb.ft.
trans X-member bolts, 43lb.ft.
Last edited by 99Bluz28; 05-07-2014 at 02:00 PM.
05-07-2014, 09:08 AM
#4
Moderator
I have stripped the weak threads in the poly trans mounts and would therefore not go above the 37 ft-lbs regardless of the bolt grade. I doubt the nut in the Poly mount is even a grade 5.
And I read literally dozens of posts here about the Poly trans mounts leading to vibration and noise complaints.
And I read literally dozens of posts here about the Poly trans mounts leading to vibration and noise complaints.
05-07-2014, 01:59 PM
#5
Yeah, with the poly mounts I'd definitely go with the lower torque spec, if you have any doubt about the grade or quality of the poly trans mount, bolt or nut.
I actually went with the lower torque ratings I found for a 7/16" bolt with 14tpi in grade 5 and 8.
I actually went with the lower torque ratings I found for a 7/16" bolt with 14tpi in grade 5 and 8.