Did a 700R4 -> T56 swap. I used a lot of information from this forum and it was a great help. I got a little carried away and forgot that I had a 383 stroker (400 crank). So had a new Ram clutch pack (88615) & Ram fLYWHEEL(798-2555). After everything was done and assembled, my first drive was not a good one. The motor shook bad (out-of-balance). I only drove it easy a couple of blocks and knew something was wrong. After further researching, I realized I bought the netral balance aluminum flywheel. I needed the externally balanced 400 crank flywheel. But @ ~$470 a pop, I was not ready to pay for another flywheel. So I carried my 400 flexplate from the 700R4 and new flywheel to a machine shop. They spun the flexplate and then modified the new flywheel with a counter weight to match the flexplate balance.

I rebolted the new (modified) flywheel and fired it up.... ran perfectly smooth all the way up to 6k. So I reassembled everything and went for my second drive . I still have an out-of-balance condition, though not as bad as before. So if I sit still, push the clutch in and rev the motor, it vibrates. This tells me it is not something in the transmission, but somehow the flexplate assembly is causing the out-of-balance condition. ... I think .

Anyone have any ideas or suggestions on what I am doing wrong?

thanks for any feedback. -Brad

 

Could be a warped or out-of-balance pressure plate.

 

Possibly, but I doubt it since it is brand new and only has about 2 miles on it. It runs smooth up to ~3k, then gets the vibration. It also vibrates with the clutch disengated and car is not moving, so I believe that eliminates the pressure plate warpage.

 

It is intersting to me that the flywheel is balanced (counterbalanced within a gram or so of what is expected), but yet the clutch pack is a cast pc metal housing which I would suspect would not be be perfectly balanced and then bolted directly to the flywheel. .... just sayin

 

I had a similar situation. When I first put the car together it had a nasty vibration. I was scared as the motor was new too. I pulled the trans and ran it without the clutch and all was smooth. So what I realized was it was the pressure plate. So I ran the motor with just the pressure plate and no clutch disc. I repositioned it each time and found where there was no vibration. Once I found the sweet spot I marked the flywheel and pressure plate and put it all back together vibration free.

 

It's worth a try. I'm getting pretty good at taking the tranny out and putting it back in ... not NASCAR quick, but ...

Thanks for the feedback!

 

Yeah I have had mine out 7 times I think. I timed it last time and it took 20 min to get out.

 

ok,I took the tranny out. I did not touch the flywheel or pressure plate. Started it up and it is smooth all the way to red-line.

So, what does that leave? Is it possible the throw-out bearing is bent as I was taking the tranny in & out a few times? would that cause a real vibration in the motor?

The input shaft on the tranny has a little play in it, maybe .005. I bought this used from someone I don't know. He told me it had 78k on it from a 97 Camaro.

I put in a new pivot bearing which didn't seem to have any problems and fit fairly snug on the input shaft

 

The only suggetion I have at this time is the vibration may be caused because I am using rubber motor mounts and poly mount on the transmission. I am considering switching to the rubber tranny mount and put it all back together ... one more time.

If anyone has any suggestions (Prior to me reinstalling ), let me know.

Thanks!

 

This is a silly question, but trying not to overlook the obvious. Did you put a new pilot bushing in?

 

I appreciate ALL feedback and ideas since problems many times are the "simple overlooked items". I do have new bronze pilot bushing. This was swap from an automatic 700R4, so there was no bushing before.

 

Saw it was a swap, thats why I asked about the bushing. just threw the new in there I guess. May want to check the ID of the bushing compared to the OD of input shaft. Possibly given the wrong one? But you said it happens when the trans is disengaged. IDK just throwing stuff at you

 

Doh I guess that would be the "pivot bearing" part of your post