[68bigblockSS]

alright i just put on a new transmission cooler and transmission mount and when i took it for a test drive i had a vibration at around 2000 rpm or so. it was so bad that i thought one of my new wheels had come loose. turns out that the vibration is there even in park when i slowly increase rpms. the motor is a 468 and the trans is a th400 when i pulled the old tranny mount it was destoryed so i put in a new energy suspension mount. could the poly mount possibly vibrate that bad?

[Skeeter55]

Man that sounds like a Flex Plate is lose or the Harmonic/Balancer is breaking apart...

[Everett#2390]

Place a 2X4 across the trans oil pan, nubolt the trans mount, jack up the trans about 1/2-1 inch.
Is the vibration still there? If so, see Skip's suggestions. If not, then the pad is hard and does not absorb vibrations.

[68bigblockSS]

ill try a cheap 5 dollar rubber mount and see if it goes away.... it was running perfect before.

[68bigblockSS]

well i put the rubber mount it and the problem is gone... seems most people have very little problem with the vibration of a poly mount but i guess mine was an exception.

[Everett#2390]

Something may still be amiss in the balance dept.....