Front Drive Shaft ?

[Papa_Smurf2]

I have a 77 K10 Stepper with a 3" lift and running 35x14.5 boggers. We went to Louisiana Mud-fest this past weekend (a must for anyone close by) and broke the u-joint clips holding the front drive shaft to the t-case twice (the mud was about two and half to three feet deep). The yoke is pretty buggered up so I'm going to replace it. Smurfette has a 350 and a 4 speed (straight) trans. I use spicer heavy duty u-joints and both times the u bolts holding the shaft to the yoke were twisted or broke off. Any ideas on why this is happening and/or how to solve it would be very much appreciated.