Steven6282

Hello everyone,
I've had a T56 swapped into my car as well as having the rear rebuilt with 28 spline parts and a posi unit.

After going through some other problems I'm now trying to figure out the problem that I've got a bad vibration coming through the shifter and clutch at over 4k RPM (in any gear). I think I can also feel it even when the car is sitting with the clutch in or transmission out of gear, but I'm not 100% sure on that part, if it is doing it then it's not nearly as bad.

The vibration can be felt most like I said in the clutch and in the shifter, but it also vibrates the entire chassis.

The mechanic that put the transmission in for me also put a new flywheel for a 97 trans am on, since that is what my T56 came out of. Is it possible the flywheel is out of balance causing this? Also my engine is externally balanced with a harmonic balancer on the front, if the mechanic used a stock 97 trans am flywheel, would that be incompatible and cause this? Or does anyone have any other ideas what would cause this?

As long as I'm under 4k RPM I don't feel it (that is not to say it isn't there, it's just not bad enough for me to feel) and everything else feels fine.

Thanks for any advice!

jmd

iTrader: (4)

I'll copy and paste from one of your prior threads:


The speed of the transmission varies from engine rpm if the clutch is pushed in. You haven't said anything indicating the transmission is at fault. Plus, in your prior thread regarding rear end noise, you indicated
which means you probably would have have noticed a vibration like this if it was the donor transmission.

If a 97 flywheel was used, then it's an internally balanced 86 and newer 1 pc. rear main seal engine with an imbalance built into the flywheel.

The pressure plate has to have correctly shouldered bolts to index the pressure plate to center. These are part smooth, part threaded. The smooth part sets into a countersunk bore in the face of the flywheel, just before the tapped threads of the flywheel starts. Did he use the right bolts? New ones? The old ones? They're discontinued @ GM but available aftermarket.

So, you didn't have the problem with the T5 - Therefore it's not the new engine.
The only parts that would vary with engine rpm are those bolted directly to it - Flywheel & the pressure plate bolted to it.

So he screwed up the PP install or your pressure plate is out of balance of the flywheel balance is defective.

Hope you're enjoying the T56 otherwise.

87CIZ

iTrader: (8)

Might not have anything to do with it. But maybe from the driveshaft? Did you put a poly transmission mount in and leave rubber mounts on the engine by chance?

Steven6282

Thanks for the reply.

Just to clarify from the previous post, the whining has been fixed with the rear end being redone again by him. It still has a very small whining noise that I can barely hear, and he claims is in the gears (3.73 richmond gears). I'll get a 2nd opinion on that later but supposedly he had a friend that builds race rear ends check it multiple times and it checked out. The vibration I was experiencing at high speeds is gone also, that one was a driveshaft problem. I don't know how but they bent the driveshaft or something when installing new u-joints on it.

The vibration I'm experiencing now was there at the beginning right after the install but he says he doesn't know what to do to fix it. I don't know much about the pressure plate and bolts but I will ask him about those as you have described it. He might not have used the right bolts because I know he had to get a new flywheel because he left the old flywheel in the donor car (which I sold already before he figured out that my 86 flywheel would not work). So he must have used the flywheel bolts from my 86, however I'm not sure which pressure plate bolts he used.

Admittedly I drove the donor car and tested the transmission, but I can't remember if I ever revved it really high. So I can't completely rule out something in the transmission itself unless this type of vibration would be highly unusual from the transmission internals. Like I said, I think I can feel it a little when the transmission is out of gear which leads me to believe that like you said it's something attached to the engine side.

This part concerns me some. This internally / externally balanced stuff confuses the heck out of me. You say internally balanced, but the specs on my engine from the engine manufacture specifically say it's externally balanced?

The bolts you mention are available aftermarket. Do you happen to have a link to the correct ones so that if I have to order them I can order the correct ones?

Thanks!

87350IROC

iTrader: (2)

Did you have the new flywheel balanced to match the old flywheel? If the new engine is balanced different, then the new setup would need to be matched.

The correct bolts look like the below pictures. I would ask your mechanic which bolts he used. But don't give him the correct answer before you ask. You will get a more truthful answer that way.

McLeod part number 1502. I searched far and wide for the correct bolts. And even bought some from other places that claimed to have the correct ones. McLeod is the ONLY place making the correct bolts. Proof is in the pictures.