Driveline angles

[63ImpCB]

Been chasing a vibration and noise for a while now in my 63. Thanks to the help of the guys on the forward look forum, I've determined that the pinion angle is incorrect. Let me give a little background before I proceed. The Imperial has a rebuilt front and rear suspension with new leaf springs and rear struts. The ride height is properly adjusted and the rear springs have around 300 miles on them. The driveshaft center support has been refurbished as well. The vibration comes in at around 25 or so mph. I have an angle finder and it appears that the differential pinion points up about 5-6 degrees. The rear driveshaft slopes down toward the rear at 5-6 degrees, which would give a working angle of 0 degrees. I found an old Chrysler Master tech a reference film that states the working angle should be between 1 and 3. I'm getting a lot of conflicting information from various websites. Most people say that the pinion should point down but I'm not really sure if this is for drag strip purposes or what. I really don't want to spend a lot of time chasing my tail oh, so I thought I would ask the Imperial experts. Has anyone had this problem? I just need a little guidance on this pinion angle. Thanks

[gary h]

I don't know if this will help but I have a set of Shims for sale for the center support I removed from a '63 Conv. years ago. 20.00 + postage.

[mikey62]

The pinion tends to want to rotate upward as torque is applied, thats why the go fast cars had pinion snubbers that were adjustable. Chrysler was smart enough to engineer these well in the first place so Id go with their recommendations even if it conflicts with websites or tribal knowledge.

[watchfatha1]

FWIW It has been my experience (20 plus Imperials) that re-arched springs almost always cause a vibration-especially if additional leafs were inserted. Note that the FSM clearly states that a bit of reverse arch is normal and is not by itself sufficient reason to replace springs. That said, I would read the section on driveshaft angles noting that both the Springs, the driveshaft carrier AND the strut bars (left and right that attach to the axle) can be/are shimmed, the latter underneath where they attach to the car-essentially making them longer and pointing the pinion up-or shorter (removing shims) to make the pinion favor downward. In addition, wedges are specified (and pictured) for insertion between the spring and the spring pad on the rear axle in order to achieve proper angularity and avoid vibration. Not having the car in front (underneath) me it is hard to predict where the problem(s) lie, but I'd first load up the trunk with REALLY heavy stuff to see if lower springs would make a difference, then go from there.
( For those reasons I NEVER re-arch springs unless there is a clearly broken leaf. Instead I install a set of air shocks and play with ride height until the sweet spot is achieved.)

Another possibility is that your driveshaft is out of phase. This can come about as a result of the shop that did the re-furbishing of the driveshaft carrier not properly observing and MARKING where the two pieces came together (there's supposed to be a dot) before they dismantled them, and just pushed the two pieces back together after doing the carrier repair without regard to positioning.

NOTE: SOMETIMES the two driveshaft pieces come from the factory at other than 90 degree angles to each other (with respect to the joints) and yet the shaft is vibration free.

I don't envy you-it is a major pain in the backside to find and resolve these issues. Have patience and do one thing at a time.

Good Luck.

[ImperialAtom]

Just a thought - since it sounds like you are trying to determine what is causing the vibration.

Maybe get one of those gopro cameras where you can mount it under the car. It can watch your drive shaft in action, so you can hopefully see where it is rattling. It may take a few different positions and angles, but it might help you narrow down what might be happening underneath.