Taken from 4crawler (Roger Brown) web page;

A lot of good info on d-shafts and other stuff on his web page.

http://www.4crawler.com/4x4/CheapTricks/Driveline-101.shtml

http://www.4crawler.com/4x4/CheapTricks/index.shtml#TIPS


For setting the drive shaft length, measure it from flange to flange at rest. You should allow at least 1.25" of compression on the rear shaft and maybe a bit more in front (1.5"-2" - assuming spring shackles in back) to allow for the suspension compression. Then, be sure you have enough spline travel at full droop. If the existing spline length is not long enough (sometime a problem in the front drive shaft) a long travel spline shaft may be needed.