poly mounts

acomaelkhunter · Oct 1, 2012

my engine rebuild only has 30k miles on it

rz5.0 · Oct 1, 2012

Had it done it since the rebuilt.. Vibrations will kill an engine pretty quick

acomaelkhunter · Oct 1, 2012

it could have been, just didnt noticed since i installed the poly bushings on the tranny.

GTR · Oct 2, 2012

have you pulled the driveshaft? if so did you reinstall it in the same clock position?

acomaelkhunter · Oct 2, 2012

pull the drive shaft out of the tranny and rotate 90 degrees? not that just the rear u-joint to axle

acomaelkhunter · Oct 2, 2012

btw. the vibration occurs between 1800 and 2800 rpms, in idle and in gear (every gear)

Musturd · Oct 2, 2012

Yea vibrations ain't good for motors when shaking a lot it's easy to end up with crank walk.

rz5.0 · Oct 2, 2012

Doubt its the drive shaft if its doing it in neutral.. I would check make sure you have matching fly wheel and harmonic balancer..

Steve-Oh · Oct 2, 2012

Here is something simple to do. Go buy a $30 factory rubber trans mount and swap it with the poly trans mount you just put it. If the vibration was caused by the poly mount then it will subside. I've already encountered this issue with the poly trans mount and when I swapped it out the vibration subsided. I also already went through spending thousands at a shop to check the flywheel, new clutch, harmonic balancer and been told to rebuild the motor when what I later found it to be the trans mount. Also if you've changed the shifter to an aftermarket one you'll notice a slight increase in vibration due to loosing the factory rubber isolator between the handle and base.

If the vibration does not subside after this swap you at least know for a fact it wasn't that and you won't be out 100's of thousands of billions of dollars trying to figure out more complex factors that may or may not be the issue.

GTR · Oct 2, 2012

acomaelkhunter said:
pull the drive shaft out of the tranny and rotate 90 degrees? not that just the rear u-joint to axle

no, there is a notch in the flange. the mark should be visiable on the pinion flange. just line it up. mine did the same thing after i let a local shop work on it. clocked the driveshaft correctly and problem solved.
or like it was posted the H/B and flywheel aren't jiving. when the motor was rebuilt what was it balanced at? stock F/W is 50oz. balanced. if your motor was balanced at 28* the stock F/W is the problem.