Originally Posted by Max Capacity
More then likely the splines on the end of the shaft are what is broken, or worn off caused by something else.
Which splines? The splines on the LH side in that pic I posted? Or the pinion teeth?
It's not possible to strip the splines on the LH side in that pic. You'd break the center diff LONG before that happened.
It's possible to ruin the pinion teeth, though. The most common cause is by people who think they are supposed to remove the front diff cap to replace the axle seal, then reassembling without properly setting lash. The second most common cause is the wrong fluid being used.
What fluid were you using? If you were using a GL-4, or something like Uncle Scotty's Cocktail (which includes Synchromesh), then there is a good possibility that you've destroyed the ring and pinion. GL-4 fluids can't handle the shear loads seen in a high offset hypoid gearset. It can also happen if you ran a GL-5 fluid, but failed to change it at appropriate intervals. You get lots of whining as the pinion and ring gear wear themselves to knife-edges before completely shearing the teeth off of the pinion. I've actually got a scar on my right index finger from where I got cut on a pinion gear that came out of a transmission running the US Cocktail.