71 Road Runner vibration- Help!

[Curious Yellow]

Hi Guys,
I made the mistake of sending my car to the body shop without addressing a vibration issue. It gets worse as RPMs increase and gets bad above 2000 RPMand you really feel it in the console and transmission hump. I know it is not driveshaft related as it does it in Park as well. Now the engine and trans are out of the car and I would like to solve the problem before I reinstall. I was advised that a cracked flex plate was the likely culprit, but when I pulled the transmission off of the engine today there were no cracks. I guess that leaves the torque converter or the transmission. I did notice that the top 4 bell housing bolts were loose and a couple were finger tight. I have not really played around too much with engines and tranmissions, I usually leave that for the pros. Do torque converters go bad and cause vibrations? I held the torque converter, input shaft opening up, and shook it back and forth and felt a clunking inside. Is that normal? Any advise you can give would be appreciated. Also if it is the trans can this be diagnosed out of the car? Thanks a lot!

[landon1]

the first thing i would do is look at your motor mounts...that's what was wrong with my car and now it's perfect...dunno what else...that's for the more trouble-shooting type

[aerodynamic]

If I recall correctly, some big blocks were balanced externally, and some internally. Is it possible you have an external harmonic balancer on an internally balanced engine? I had a 440 once that I put together that always had a severe vibration like that, but sold the car before I was able to prove the theory. And yes, the insides of a torque converter feel loose.

[Curious Yellow]

Hi Guys,
Thanks for the responses. I knew when I bought the car it had a later model 727. When I pulled the transmission off of the engine I found they used a late model torque converter on the engine. My engine is a 1969 383 with a forged crank and the torque converter was a 1976 for a cast crank and has extra weights. Bingo!! A few of the transmission bolts had backed out as well, so hopefully this is the solution.