What the heck am I doing wrong? LS1/T56 driveshaft vibes.......

[Kokamo]

Hey guys, I have a 69 Camaro with an LS1 and a T56 trans. The car originally was a 6 cyl powerglide. I used the factory mounts.....I don't know if the motor (frame) stands are different from the V8's. I bought my car with a small block so I don't know if they have been changed.

ANYWAY, I had the stock 8.2" rear end with open 2.73 gears......I swapped it out for an 8.5" with 4.88 gears......and now that the driveshaft is spinning much much faster, thats when I found out I had a driveshaft issue. After long hours of looking for bad bearings, u-joints, driveshaft ballance, bad gears, bent axles and any other thing that could possibly pertain to a vibe.....besides driveshaft angle....I found no problems with anything. I even had the driveshaft re-checked at two different driveshaft shops.

So, I swap back to the 8.2" rear end and run up to speed on jackstands and notice I have a vibe with a complete different rear end other than the 8.6". So, after going up and down on the pinion angle at all degrees, I havent found an angle that will get rid of the vibe. So I finally realize the motor/trans is waaay low in the rear making the driveshaft angle not correct......so to speak.

I can't go down in the front due to a custom rack and pinion steering setup, so my only option is to go up in the rear.....which I have done and it changes nothing at all.

I know that there have been many LS1/T56 swaps out there, and I'm sure there has bound to be somone that has run into this issue before. Can anyone spread the light on this issue? Please?

Sorry for the long post, thanks for taking the time to read if you got this far.

Joe

[CarlC]

What are the details of the driveshaft? Diameter? Wall thickness? Length? U-joints? etc.

[MrQuick]

To start the 6 cylinder frame stands are way different. Im suprised you got them to work. The holes will sit the engine too low.

1st off get the correct motor mount stands and go from there.

Get the correct trans cross member and mount to put the T56 tail shaft where it needs to be.

[Kokamo]

What are the details of the driveshaft? Diameter? Wall thickness? Length? U-joints? etc.

Stock 69 Camaro driveshaft shortened 1 inch. Di ameter seems to be around 2-1/4" maybe? I have no idea of wall thickness. U-joints are Precision greaseable part number 369.


To start the 6 cylinder frame stands are way different. Im suprised you got them to work. The holes will sit the engine too low.

1st off get the correct motor mount stands and go from there.

Get the correct trans cross member and mount to put the T56 tail shaft where it needs to be.

I'm almost positive I have small block mounts because thats what the car had in it when I bought it. They are in the stock location with stock small block motor mounts bolted to a plate just like an ATS plate mount.

The crossmember is custom as well. I even experimented with the X-member off and the trans down and up as high as the body would allow and still no fix.

Joe

[CarlC]

At what driveshaft speed does the vibration start, and does it increase as shaft speed increases?

The exact diameter (to within 1/16") is needed. No guesses here, it's one of the major factors influencing the harmonics.