Severe clunking when pressing Brakes going down hill. Please help!

So i took the xj off road for the first time since break in on my regear and rear spartan locker install. I have never had a locker before so i don't know what to expect. It could be normal but my car started shaking.

I was going on a somewhat steep decline and i press the brakes harder to slow down. It seems the brakes were not locking up. But the rear end was clunking badly and i did not want to stop well. I thought my axle was going to explode and drive train fall out it sounded so bad. I was able to repeat this 3 more times. When i was driving on less of an incline it did not happen and i could stop properly.

I am thinking maybe one wheel is locking up better than the other and the locker is whack'n out. Please give me some direction i am concerned about blowing up the rear end i just put all this money into.

Thank you,

XJNate

I did find a pinch in my rear brake line on the axle near the splitter block. But fluid flows and bleeds normally.

were the axles out of the vehicle for the re-gear? did you use new u-bolts and then re-torque them 100 miles later?
maybe the incline transferred the weight of the vehicle enough to show you a lose axle?