The vibration is definately worse under hard accelaration, if I just ease it up to 3500 rpm in third I feel it but not nearly as bad. I'll pull the driveshaft and have it balanced to start. Thanks again
Under hard excel the pinion wants to rip itself from the rear and ride up over the ring, causing it to move the housing up....
When that happens, it can change the joints angle up to 4 degrees or more if the power is there and the springs are weak...
So if your angle is say 2 degrees different then shaft, you'll be susceptible to pinion angle vibes, meaning ..... if the shaft is at 0 degrees and the pin is neg 2 degrees, you'll have a problem.
or if the shaft is 2 degrees and the pin is 4 degree.
When you launch or excel hard, the pin will jump up 4 degree's putting it out beyond the positive side of acceptable...
(we are discussing a leaf spring car so do not even bring any other type suspension into this, each suspension is different)