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pedro
02-18-2011, 09:14 AM
I am struggling to get rid of this vibration that I believe is driveline related. The car is 69 camaro w/ L92, T56 Magnum, Inland Empire aluminum driveshaft, Moser 12bolt rear, AME front clip, and Airbar modified by Prodigy.

The vibration is speed dependant occuring 75mph and up (I have been running on the lift up to 120mph). It is worse under acceleration and I don't really feel it during de-acceleration.

I have eliminated wheels and brakes by removing them, ran it without the driveshaft to eliminate motor and trans, and had the balence checked on the drive shaft.

The angle for the trans is 4deg tailshaft pointed down. Driveshaft is 0deg. Pinion I have tried from 3deg front pointing down to 4deg front pointing up in 1deg increments. All were the same except 4deg up where it seemed to be slightly worse. I am using an analog angle gage measuring at the yoke (yoke is same angle as damper), center of DS, and pinion flange. With that much varation in pinion angle I thought I would see some change in vibration, but only the 4deg was there any noticeable change.

I marked ont the centerline of the engine/trans and ran that all the way back to the diff. The pinion flange was only 1/4in off the centerline. It seems everything is inline but I also moved the rear right and left up to .5in with no chage in vibration just to make sure.

I am thinking the trans angle needs to be closer to 2-2.5 since the ds speed is so high at those speeds (3200rpm and higher). I did mange to shim it to 3.5deg but any more will require cutting the trans tunnel for clearance. At 3.5deg for the trans the vibration was the same as 4 deg (I used the same varation in pinion angle except I stopped at 3.5deg up).

So do I cut the trans tunnel and go for 2.5deg or is there something I am missing??

Thanks
Pete

CamaroAJ
02-18-2011, 09:31 AM
are you set at ride height when testing this?

pedro
02-18-2011, 10:01 AM
are you set at ride height when testing this?

Yes, I use jack stands under the rear and measure eye to eye on the shockwaves to get the correct ride height.

Pete

Josh
02-23-2011, 10:35 AM
Does that T56 have a bearing in the tailshaft housing?If it does and it is out of round then it will wobble regardless of what you do.
Another thing- I had vibration issues in a '68 that I was able to change a little but not go away. I had my shaft balanced at a local place that has a machine. I went on Power Tour and it got so bad in Indy that I could not go over 45mph! I found a shop in indy that made stuff for race cars and they said it was my shaft and straitened it. Now it runs smooth as ever. My point.. Inland makes a good shaft but perhaps you can beg, borrow or steal a shaft from someone and test it again.

ErikLS2
02-23-2011, 12:54 PM
I would vote for trying another driveshaft too if you can get a hold of one. Also, when you take it out, , move the u-joints around, they should be nice and smooth. A sticky spot in one of them gets amplified when it's spinning real fast and can cause this kind of vibration.