NotAClue

I'm about as clueless as a driver can get, but the mechanic can't get this right either, so here goes.

mechanic puts used rear axle put on my '96 Grand Cherokee after original damaged, drive 50 miles and a grey cloud of smoke comes pouring out from rear of car, drain plug missing from rear differential.

mechanic thinks maybe he forgot to put it in, adds new one, tops off gear oil and sends me on my way.
45 miles later, Jeep starts handling odd, I start to pull over and drain plug blows out, gear oil everywhere, the 'grey cloud' again.

This time he finds vent hose disconnected from vent, replaces vent and hose (his words, not mine).
40 miles later, the infamous 'grey cloud' again.

What is causing this big buildup of pressure that forces the drain plug to blow out and gear oil to spew all over the back of my Jeep?

dave1123

I think there is too much heat building up so that the gear oil is boiling. The gear lash on the ring and pinion may be set too tight or the pinion bearing lash is too tight. Either way, the used axle is at fault.

JBimmolate

Is the vent tube clear? If not it could have popped out the plug and popped the vent hose off at the same time.

Miles