'86 Jeep CJ7 - need help

I have a 1986 Jeep CJ7 which I recently put a rebuilt engine into.
Just today, there's a new problem that's got me stumped. The two rear
tires have a greasy oily substance that is literally sprayed all over
them (inner tires and inside the wheel wells). I've been underneath
and don't see any leaks - this obviously happened while driving.
There's a ton of oil. What is the most weird is that it's on BOTH
sides - both rear inner tires & wheel wells. Brake fluid is full and
looks fine, no drips underneath the jeep. I did hear a semi loud clunk
when driving this morning just as I got going and was turning sharply
out of the driveway. No leaks up front.

Any ideas?