U-joints. Tight/loose/sloppy vibrations

In diagnosing a vibration issue above 70mph, I have checked my pinion/transmission angles and they are spot on as far as having correct angles and diveline alignment.

I took the driveshaft off and began to play with the u-joints. The front transmission yoke joint moves very freely. It flops around and seems well lubricated. There is no play as far as twisting goes, but there is maybe 1mm of movement up/down on an axis of the u-joint. Could this be the cause of the vibration? Is the general rule of thumb, NO wiggle movement?

Also, the rear u-joint is almost feeling like it is seized up. I grab it and it takes a good amount of effort to get it to rotate on either axis. The grease inside is black and smells like someone took a crap in a bucket of hot tar.

I am replacing the rear for sure, but is the front suspect?

ForceFed70 said:

The movement you describe on the front joint sounds like the U-joint cap isn't seated deeply enough. You may be able to fix that movement with a hammer and a couple of correctly sized sockets. I kinda doubt that it's causing any problem tho.

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I just took the front u-joint off, cleaned it up, and reseated the caps. It has no movement at all.

I just measured the pinion and transmission angles again. The rear axle angle is +2.5 degrees canted up, and the transmission angle is -1 degree canted down. I am going to shim the rear axle where it mounts on the leafs or put spacers on the transmission mounts to correct the transmisison angle.

This is with a T5 swap and crossmember, I think the vibrations are from the different in angle

Correction in angles.

The driveline has 1 degree up
The rear pinion is 2 degrees down
The transmission is 1 degree up

I was going to raise the rear of the transmisison 1/4-1/2 inch to make it get 1 degree down hopefully to be within 1 degree of difference and hopefully get rid of the vibration, but the T5 can't move up anymore without hitting the trans tunnel reinforcement. I do not wish to notch it, so I am going to shim the pinion with a 3 or 4 degree shim to get within 1* of "perfect" driveline angle, instead of the 3 degrees difference I have now

Rapid said:

Please keep us updated. I am fighting a similar vibration with my T5 setup.

Thanks.

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I have 1 inch lowering blocks in the rear between the leaf and the axle, I measured and milled some off so that the block is now both a lowering block, and an angled shim. This corrected the driveline angles, and with a test drive I hope that the vibrations are either much better or completely gone