[hylander]

1990 Extra Cab., 2 Peice driveline with double carden joint.
Right now there is a 10 degree differance, I have read that the axle should be
1-1.5 degree's so that it will be zero when under pressure.
If this is correct I would need say an 8-9 degree shim, however when shimming the pinion moves higher and thus not requiring such a high degree of shim. Am I understanding this correct ?
I don't want to buy several differant shim's experaminting

 

[dcg9381]

The best way to do it would have been using an "angle protractor" - one of those magnetic deals that you can slap on your 3rd. The triangulate the geometry of the truck before and after the lift.

Not good at geometry? The rule of thumb that I used for my front axle end rotation was 1.5 inches of rotation per every inch of lift. The front has a shorter driveline, so 1.5 inches might be too much for the rear. I'd go with 1 - 1.25

Other things to consider: Did you change shackles? If you shackle up the rear - as most rear spring swaps do (esp the Chevy's) - this helps rotate your pinion.
On my truck, with the shackles, I used a 3 degree shim...