Hey y'all
94 f150 4x4 4.9L, m5od trans, 4inch body lift, 2inch suspension lift. 230,000miles
Rear diff has an Aussie locker.
My problem is when from a dead stop if I don't ease off the clutch very carefully I get a loud clunk that definitely feels like it's coming from the rear end.

Climbed under the truck yesterday and am able to spin the rear drive shaft about 1-2 to 3/4 of a turn. Seems like a huge amount of play. Popped the rear diff cover off and everything seems okay, no metal shavings anywhere. I'm not very experienced with the Aussie locker at all so maybe it could be that? But it was installed 2years ago by a very reputable shop. So I wouldn't so. U-joints are new, no slop in those bad boys. Trans and transfer were both rebuilt about 2 years ago as well. When I changed the slave cylinder a couple weeks ago i checked the splines on the shaft at the slip yoke and they're not worn at all. Even put some grease in there before re-installing.

The trans does feel like it's getting tired, if I don't shift at just the right rpm I'll get a little grind going from 2nd to 3rd and from 3rd to 4th. My guess is the trans but maybe you guys have some other suggestions? As always any help is greatly appreciated.