Just checked the two u-joint angles and they were bad mismatched and causing vibes. No surprise there.

I have now adjusted the TA so that the (pinion to DS) and the (tranny shaft to DS) angles are the exact same or parallel. This gives me a 4 degree angle on each end of the DS. Did this with a magnetic angle finder and a bubble level.

Drive shaft is 0 degrees on the guage. Pinion is +4 (down from DS) degrees and tranny shaft is -4 (up from DS) degrees.

Have not driven it yet. Hope this helps.
Thoughts?

 

If your running -4 degrees pinion angle, even with a M6 I believe that's a bit to much. What do I know though. Happy new year.

 

What is more important. To have the tranny output shaft and the pinion parallel, or to have the DS to pinion angle closer to 2 degrees?

 

The "negative" pinon angle is there to compensate for the movement that takes place in the torque arm under heavy torque load. Getting it aligned correctly under no load is not the same. The pinion moves upward under load. How much depends on the structural rigidity of the torque arm, and the type of connection at the front of the arm. A rubber or poly bushing (or bushings) in the front is going to allow more movement under compression, compared to a spherical rod end, and requires a greater negative preset under no load. Then there's the engine/tranny assembly, floating on rubber (or poly) mounts. A system that is set with the tranny output shaft and the pinion shaft parallel under no load is not likely to maintain that condition under heavy load.

4-deg difference may cause excessive u-joint wear under normal driving conditions. I know Steve Spohn recommended no more than a 2-deg diff for street driving, while 4-deg may have been required under track conditions. He recommended resetting to 2-deg or less after a day at the track. I suspect recommendations like this are based on emperical results, and not on an in-depth analysis of the multiple-link mechanism that the system represents.

The ideal setup would be a drivline that is perfectly straight/parallel (trans output shaft through pinion shaft) under maximum torque load.

 

Update.
After continued frustration following the instructions provided on the net, I decided to simply revert back to what has always worked for me when I had I had a 4" jacked Jeep wrangler with a 24" long drive shaft and 13 degree u-joint angles. Anyone who has ever been down that road knows the PITA that is to correct.

What I always did on my Jeep was ensure that the tranny output shaft and the pinion were absolutely parallel and to hell what the driveline angles are.

It has alway been my understanding that if both u-joint angles are equal then there can be no vibes due to cancellation. Also if the two angles are equal then the tranny output shaft and the pinion must be parallel. When one u-joint angle is 2 degrees and the other is 4 degrees then its vibration city due to the tranny output shaft and pinion NOT being parallel.

So what I did was toss the angle finder and get out the adjustable bubble level. I placed it on the front of the harmonic balancer and adjusted the the bubble to centered on the dial. Of course we all know that the crank and tranny output shaft must be parallel so this was the easiest place to get the reading from. I then took the bubble level and placed it on the face of the rear end housing where the gear case bolts up. I then simply adjusted the TA till the bubble was centered. The tranny output shaft and the pinion are now absolutely parallel.

I got the angle finder out to see what the driveline angles were now measuring out at, and they were both sitting on +3 & -3 degrees and the drive shaft was sitting on 0. This is exactly how I set the driveline angles on my Jeep and it never failed then.

I drove the car and 90% of all the vibes were gone, especially the vibe that prevented me from going over 60MPH cause it felt like the car was going to explode. I know that if it ain't dead nuts on right now, then it must be very close. At the very least, it is now drivable.

I then adjusted the pinion both up and down a single degree to try to totally dial it in but it made no difference either way so I locked it down and called it quits.

The drive shaft is balanced and the bad u-joint was replaced so I must assume that the DS is not causing the very minor vibe that I still hear and feel. I am also going to assume that the driveline angle is acceptable as well.

What are the other possibilities that might cause a very minor vibe to remain like this?

 

Just to double check, why not throw a different DS in the car just to make sure that's not it.