Outer Limits 4x4 Board

Hi
This is a weird one, acouple of times each year i go away , my car is fully loaded with boat in toe and boat fully loaded as well, and on the trip their is a big hill and on the way up the hill on the other side at 100ks, their seams to be a slip and the engine revs,(auto gear box) its only happens in this one spot, has anyone ever had this problem, is it belts in the auto slipping ?
its a 80 series 4500 petrol, automatic,

the angle of the hill could be causing a small problem with oil flow in your transmission.

ok and add speed to the angle, that mite be it,

yes, speed and the length of time it is on the angle.