8/34 rear end vibration and knocking

[Kevin71]

I have a pretty bad vibration when I am going down the road at 65 70 and push in the clutch.  I went to a 5 speed tremec changed the drive shaft.  I also replaced the chunk with a used one, put new green bearings on the axles. Put Dr Diff leaf spring relocators with new heavy duty springs.  I jacked the car up this weekend and put it in third.   Look underneath and the drive shaft is vibrating up and down at the rear u joint along with the yoke.  And about every 3 seconds I am getting this large clunk sound and the rear end seems to jump.  I had the rear end on the jack stands so there would be the weight of the car on the axle.  I also had the front off the ground at about the same height.  Could there be a combination of things going on.  Maybe not enough pinion angle and something wrong with the chunk or pig. When I first put this back together there was a vibration.  That turned out to be too short of a drive shaft and the whole thing was shaking badly.  Got a longer drive shaft but now I have this new problem.

[Chryco Psycho]

are the brgs loose supporting the pinion gear , do you have a angle finder to measure the pinion angle , the nose of the pinion should be 5-7* down from the driveshaft angle

[Kevin71]

I picked up angle finder today and I'll try checking the pinion angle.  How do you know where to put the angle finder.  There doesn't seem to be a flat surface anywhere.

[422STROKER]

Put it on the u-joint cups.

Tom

Just rotate the driveshaft to do both angles.

[Kevin71]

Pulled the rear chunk and had a mechanic look at.  Says there is nothing wrong with it that it must be the pinion angle.  The transmission is a 5 speed tremec and has a downward angle of 6 degrees.  I put the angle finder on the bottom of chunk where it is flat and sticks out toward the trans.  Maybe the pigs nose.  It looks like it would parallel the pininon.  Anyway it is at 2 degrees up.  This is with the weight of the car on the rear end.  So now I am trying to find a local shop that might be able to do this kind of work.

[Chryco Psycho]

you can install a shim from a 4 wheel drive shop to tip the nose of the diff down, install tham  between the spring & diff seat