Anyone do this? I have the 2" drop shackles and 1" drop springs up front and was told my pinion angle is wrong. I am also thinking about removing the 2" shackles and installing the 4" JLP ones. Will this help or hurt my pinion angle? I have both the 2deg and 4deg shims but not sure how to install. It looks like the springs have to come apart but not sure. I know they go on the underside of the spring but do you have to remove the dowell from the center?

 

to install you unbolt the u bolts holding the axle to the springs, jack the spring up or drop the axle, either way...you'll probably have a lift. Anyhow, just take the shims and put the fat part towards the front of the truck so that it rotates the axle housing downward, basically where the driveshaft enters the rear, your gonna want that part to rotate down. As to what degree you'll need, i have no idea about that stuff. but i'd assume the 2 deg. I think its 2 degrees for every 2 inch of drop if remember correctly

 

Neg. 4 degree's pinion angle seems to be the best for our trucks with 600hp or less. Here's a decent article on pinion angle:
http://www.carcraft.com/howto/91758/

 

The spring pack is held together with a round headed bot and nut. Grab the bolt head with Vise-Grips and unscrew the nut and install the shim into the spring pack accordingly. I'm guessing that's what you ment by "the dowell". My 2003, which has a higher GVWR and is also about 3 inches higher in the rear as delivered, came with a shim bolted to the bottom of the spring pack. When I lowered it, I simply reversed the shim and all was well.

 

That's a good article

 

That's a good article