Before you going spending all that time and money yankin the motor and
trans, lets look at the facts. The only fact is it does it only when
climbing steep grades. This to me sounds like an over heating problem
with the trans. Take the trany cooler off the back of the tranny first.
carefully separate it from the trans so you don't get the oil bath.
Bring it out to the bench and inspect the bolts. The bolts have holes in
it to let the oil and coolant flow thru. Chances are when you look into
the holes you are going to find little bits of rubber O-ring stuck in
the holes blocking the coolant flow and the trans is over heating and
puking the fluid out of the dipstick. This is an easy job and should be
performed before surgery. If it's clean and no blockage, pursue other
avenues. PS buy the 2 O-rings first. Just trying to help