I just changed out my transmission to a TH 350 (new flex pplate and torque converter as well). When I start the engine in park I get a vibration? I followed all the installation steps closely and the only thing I can think to do is rotate the torque converter on the flex plate? Any suggestions?
TCI streetfighter
Boss Hog torque conveter

 

Some flex plates (flywheels) are weighted. Depends on the engine size and if it's internally or externally balanced. If you got the wrong one it will vibrate, same with harmonic balancer. I doubt that spinning the converter will help but its worth a try. Jeff

 

I have a 396. Would that matter? The fly wheel is the same size and shape of the one I took out when it was a powerglide.

 

It is not the size, it is whether it was intended for an internally balanced engine or an externally balanced engine. Flywheels & flex plates for internally balanced engines have no effect on engine balance, the ones intended for externally balanced engines are offset weighted to counteractengine unbalance.

 

I thought that BB were externally balanced and the small blocks were internal.

 

That is usually the case, but there are some exceptions, such as the 400 inch small block which is externally balanced. The other exception is if an internally balanced engine happens to be out of balance after being assembled, the factory will bring it in balance by making corrections to the front balancer. So you canhave an internally balanced engine which is also externally balanced.

 

Well, always follow the changed items.
In this case, the Flexplate, Torque Converter and Transmission.
I doubt the Torque Converter is out of round so skip that one. That leaves you with the Flexplate and Transmission.

The Flexplate could be turned to offset the vibration and since this is a BB, external balancing is typical. The other option is the Tranny, not the internals, but the mount. If you don't have a new mount or a poorly modified mount, since this is a change from another model of Transmission, the mount may be loose, sending vibration through your driveshaft and rearend.

These obviously are just ideas, you'll have to search and test for yourself to find the answer.

 

did u check on the mm?

 

Well, it was the flex plate. I pulled it back apart and re-installed the old flex plate (after a close inspection). The car runs great with the new TCI TH350. I now just need to change out the rear end from a 273 to a 308LS. By the way I'm pulling around 2200 rpm's at 70 mph (396-th350-273 rear and 15" low profile)Thanks for the feedback.

I was told when I bought the flex plate that a 396 was interally balance, that does not seem to be the case. From what I understand is that most BB's are externally balanced and most SB's are internal.

 

It's good to hear you got it fixed.