Flip kit - pinion angle - (leaf springs)

[Slammed67]

If a flip kit is installed on a leaf spring rear suspension, is there any need to adjust the pinion angle from the factory setting? The angle relationship between the trans output shaft and pinion would remain the same, although the angle between the two would increase.

[dieselarmy13]

I didn't do any fancy dancy measurements when I flipped mine, but the driveshaft had a BIG angle to it, and after 300 miles, fried my U-joints. I knew I needed to shim it, but got busy with work and whatnot at the time. I ended up shimming it with 1/2'' shims and haven't had any problems since.

[Slammed67]

The truck in question is a 2000 GMC, short bed, regular cab. I think my u-joints are slowing getting fried as well, especially since I've had sand bags in the bed for better winter traction.

[Hertzdaddy]

The flip kit on my 73 Blazer also has a spacer with an obvious angle to it. I bought it this way so I don't know the exact specs on the spacer but it puts the pinion at 0* at ride height. I did an engine swap and shimmed the tranny to 3-4* down in the stock location and alignment is fairly close. It hasn't been running since I purchased it so I don't have any experience with u-joint wear yet. I now some drag racers rotate the diff pinion downward for better traction but it eats u-joints and vibrates in that position.

[Slammed67]

I did some research online last night and the consensus seems to be that the trans output shaft and the pinion shaft should be parallel, which would put them at equal but opposite angles. So, if the trans shaft is pointing 3° down, the pinion should be pointing 3° up. Also, the pinion should be an additional degree or two negative to compensate for the pinion (axle) rotating upward under acceleration and load. Now that the weather is warming up (from the single digits to the 30's-40's) I'll have to pull the truck in the garage and see where I'm at.

According to this website....
http://www.drivetrain.com/parts_cata..._problems.html

Ideally, the operating angles on each end of the driveshaft should be equal to or within 1 degree of each other, have a 3 degree maximum operating angle and have at least 1/2 of a degree continuous operating angle.