I have one in my 9 1/4 truck axle. the first time I drove it I had a loud pop and thought for sure it broke something. nope. just slow speed and tight turns on pavement tends to lock it and it bucks slightly and pops now and then. that popping is the teeth locking together and is more often with the manual trans than the auto trans. once I drove it and got use to it I have hammered it hard for yrs now. I have done burn outs pop the clutch @ 4500 rpm, bang 1 & revs stuck in mud as hard as I could hammer it. IMHO well worth the $ and effort to install. way easer on the bench than on your back under the truck/car but it is doable.

I am not scared of it making noise now and just hammer down with it, and I hardly ever get stuck in the truck off rod with it in the rear-end. my buddy has one in his Toyota 4x4 and it does the same thing and works fine.