lowered 64 c-10

I recently had my 64 c-10 lowered 3 inches in the front and 4 inches in the rear. when you lower a truck do you usually have to shorten the drive shaft any. Now, the rear seal in the tranny is going out. Looks like the shaft may have went in to far? and suggestions?

that would make sense, since the shaft points down at normal height and would level off at a lowered truck height. i would find a custom hot rod shop or body shop in your area and have them take a look at it and see what they think about getting a shorter drive shaft

Drive shaft length is likely just fine. You DO however correct your pinion angle. Cut the spring perches off the top of your axle housing and weld them back on at the right angle. Check out this article. http://www.carcraft.com/howto/91758/index.html