High Speed Vibration
 

How do you pin point a vibration that is only noticeable at around 90mph and up? I damn sure ain't taking to a mechanic and telling him to try. I can't tell if it's a tire out of balance, or something in the drivetrain, or where at in the drivetrain if it is. Steering feels fine, bushings should all be good, nuts and bolts are all pretty tight. Only thing I can think of is maybe something from the clutch to the driveshaft. But I don't want to take off the trans just to poke around at the clutch.

if it's happening on speed up and slow down and only at 1 wheel speed then it's almost certainly driveshaft. If you have the torque arm installed, make sure your pinion angle is right AND that the tq arm is square in the chassis.

I'm betting driveshaft. Rotate it by 1 bolt hole and see if that makes it worse or better.

I need to check over the pinion angle, I think that is the culprit. The vibration gets worse as speed increases only becoming fairly noticeable at around 90mph. I'm thinking the pinion angle is causing the U-joint phases to become noticeable, if you understand what I'm getting at.

What do you mean by square in the chassis for the TA? I know the cross member is square and even from side-to-side between the subframe connectors. However, the TA itself is about two millimeters closer to the driver's side at the axle end. We had an issue getting it to slide over and didn't think a few hairs widths would make a world of difference.

Yeah, the bearing thing I get. Most people don't know about them NEEDING to rotate or burn up. That's why chebby ford and dodge all set up the engine and rear end to be offset from each other along the long axis centerline. Causes the bearings to turn.

To center the TA in the chassis, you need to measure from the inner-rear k-member bolt to a fixed point on the end of the axle (I used a particular lug clocked to a specific position). Just like centering a k-member you need to make the measurement from one equal to the other. To put it simply, triangulate the axle housing to be square with the front wheels and chassis.

I've been working on setting my pinion angle today. My transmission output angle is 5.00 degrees (pointing towards the ground), my pinion flange angle is 1.50 degrees (pointing towards the ceiling), so that is only a 3.50 degree difference, and in my mind, not enough to cause the vibrations I'm seeing. I may be wrong but I would only think I'd be seeing that much difference if it was way off. I want it to be about 1.50-2.00 degrees so I'm going to change it and hope for the best. The driveshaft angle, was 1.00 degree, although it doesn't matter.