Pinion angle ????'s

[Leadfoot]

I need to know if anybody knows the correct pinion angle for my 68 GMC. Its a 2 wheel drive, half ton with leaf. I can't find anyone with a cheap rearend so I found a rearend out of a blazer but it was 4 wheel drive and the spring perches are 2" shorter than whats on my truck. I have a buddy with a off road shop and he said he would weld new perches on if I could find out what the pinion angle would be. Anybody know what it is?

[crazy longhorn]

Do you still have the original rear diff? if so, you can set the pads level, & check pinion angle with a cheap angle finder (Sears, or Lowes).......then set the new diff up the same. Another way you could go , is to set the diff up loosely under the truck, & check angles (with the weight on the wheels). The sum of the trans angle + the pinion angle should equal a straight line. In other words, if the trans is pointed 4 degrees down, the pinion needs to be pointed 4 degrees up to get the line angles right on. Good luck,crazyL

[Glen]

Thats right, just remember equal and opposite. If the trans is pointed down -x degrees the pinion should be pointe up +x degrees.......preferrably in the 2-4 degree range

[Leadfoot]

Thanks a bunch, now I can drive without fear of my rearend blowing up! Not to mention rattling my teeth out.

[Speedster 229]

How does the pinion angle thing work with a two piece driveline??
Seems the carrier baring holds the end of the front shaft in a fixed position so that should be treated as the end of the trans if you will so if it is 4 degrees down coming out of the carrier baring then the diif. would need to be 4 degrees up. Correct???

[crazy longhorn]

That is correct Speedster, the front half of the 2 pc shaft should be the same angle as the trans(if the trans/front half of shaft is 4 degrees down, the pinion should be 4 degrees up).