I am trying to finally get rid of a vibration that is driving me nuts. I have a dana 60 that has about 7500 miles on it now. I installed a Tick Perf viper mainshaft conversion tranny in my car the same time I did the dana with Strange's seamless chromemoly driveshaft. Ever since I did this, I have had a vibration I cant seem to kick.

I have had the driveshaft high speed and low speed balanced, so that shouldn't be the problem. over time, it seemed to get better, until recently. I was developing a clunking, and upon inspection, the rear ujoint had play. I changed that out, and now the vibration is back worse then ever! from 75 on up it starts to vibrate, and gets progressively worse as I increase the speed.

I just balanced the tires, and I have run the car with the rear on jackstands, and the vibration is still there.

I think the worn ujoint may have masked the vibration, and installing a new one made everything tight again and the vibration is back with a vengence.

I have fought with this for some time now, but since I never go over 75 I have pretty much lived with it. But now I want to take it to the track, so the vibration has to take a hike because it just isn't right.

I have talked to Tick, and they said the tranny shouldn't make a vibration. I agree with them, but I did install this at the same time.

I have been playing with the angles of the driveshaft, and here is what I got:

Tranny angle is at 88.5 degrees
front of the driveshaft is at 91
rear of driveshaft is at 91
rear end pinion is at 89.5
All of these angles dont matter until you compare them:

I have shimmed up the tranny to get the tranny at 88.5, and when compared to the front of the driveshaft, this is a difference of 2.5 degrees. I have read that you should shoot for no more then 2 degrees, but I have already shimmed up the tranny as far as I could (the rubber mount on the top of the T56 is almost touching the tunnel now)
the rear of the tranny is only 1.5 degrees off from the rear, so I think that is ok.
The pinion has -1 degree built in difference from the tranny.

I think this is all pretty good, isn't it? If not, what should be changed?

This vibration is deffinately a speed-related issue, and not a motor RPM issue, as it comes on at 75. It doesn't show up hardly at all until that point.

AS a side note, this is the second time I have had to replace the rear ujoint. the front ujoint is still the original from strange engineering. Should I chage that one out too? It doesn't seem loose though.

I do have polly motor mounts and trans mount, but I have had a rubber tranny mount too recently and it still vibrated.

Im at a loss here. Like I said, this has been present since I installed the damn thing, and I dont know what else to do...

Thanks for your help and insight...
Cody