T56 swap vibration issues

[Ray Labrecque]

I have a 69 coronet r/t iv been building and driving highschool. I swapped a t56 from a rolled viper, built a 383 big block and bought the QuickTime blowshield for mate the t56 to it. Iv checked everything and Connor get rid of a driveline vibration after 60mph. I had a driveshaft made, motor is balanced correctly and checked pinion angle and still can't figure it out please help

 

[747mopar]

Go back to the pinion versus driveline angle and look again. Been down the same road chasing a 60 mph vibration after installing a T56, mine however was there before the swap and only got worse because the gear swap lowered the rpm range at which the vibration came in.

Lift the car where your checking angles with it fully weighted on the rear axle (jack stands under the axle will do). I then lift the front to get the rockers level, mostly so you get repeatable measurements if you have to come back to it again. Pull the driveshaft so you have a good surface to measure the pinion angle (I check it at the yoke with it facing up and down with clamps removed) with an accurate tool (you can download a Clinometer app that works great for a smart phone). Then you'll measure the tranny angle at either the tranny output shaft, crankshaft pulley, bellhousing, etc... anything that is machined true to the crankshaft centerline will work. You'll want to shoot for the 2 to be parallel to one another, if your tranny is pointing down 3 degrees then point your pinion up 3 degrees.

When I was struggling with mine the tranny was 3 degree down (pretty standard) which is where the factory 727 was but the aftermarket springs I had bought were fairly stiff and had the pinion at 0. I tried 1.5 degree shims to no avail and eventually bought 3 degree shims............ I couldn't believe how that extra 1.5 degrees cleaned it right up. A good indication that the pinion needs to go up is if the vibration settles under hard acceleration and get's worse as the load is removed like cresting a hill or just easing off the gas. Good luck

 

[747mopar]

Here's my thread from when I was dealing with my vibration issue, may be of some help. I think page 3 is where I finally got it.

http://www.forbbodiesonly.com/moparforum/threads/the-vibration-that-wont-quit-whats-next.93476/