After installing a new polyurethane trans. mount I now notice an engine vibration that starts at 1800 rpm and goes away at around 3000 rpm. I get the vibration in park, neutral, and going down the road. I think it has always been there but now it seems worse with the poly mount. So far, I took off the serpentine belt to see if it were any of the accessories and disconnected the flex plate to see if it was the transmission. The flex plate looks good and the batwing weight is still there. The harmonic balancer looks good and is not loose; however I am going to change it anyway even though I don’t think it bad.

My question is where do I look next? It feels like a rotational vibration. The engine mounts are not that good but the engine does not jump when in drive. The engine was rebuilt and has about 85k on it. I reused the lifters and cam which have about 165k all the other wear items have been replaced including the crank. This is driving me crazy! Like I said I think it has always been there but I have not driven the car in year and just installed the new trans. mount so now I really notice it. Any help appreciated!

 

mine is doing the exact thing ,all i put on it is a poly trans mount ,gonna pull it off sat. to see if it quits ,ill let you know,later jimmy

 

from what i found on other boards poly mounts are taller and you need to shim the xmember to make the vibration go away.

 

Interesting, but I am not sure that is the problem because I still get the vibration in park. I also disconected the flexplate from the torque converter and it still does it.