Rear end temp

Just out of couriousity, has anyone evey felt there rear end housing after ....say a 30 mile drive ? I put a set of 4:30's in my 8 3/4 and after about 30 miles rolled under the car and felt the backside of the rear pumpkin and holy **** , nearly burnt my hand. they shouldn't get that hot should they. They are a 742 case powerloc ???