Rear differential overheating on hard pulls
 

when pulling 36 foot horse trailer in mountains rear diff gets super hot and pushes fluid out pinion seal. diff not noisey and very little play when drive shaft rotated.
Mabe heavier diff grease?

I have no idea what a seadiff is but I assume you were referring to the pinion seal? I wonder if your axle vent tube is plugged?

I have seen where a pinion seal is leaking badly but rather than replace the seal someone has drained the oil and actually put grease into the rear end just to sell the vehicle. The oil should be a synthetic gear oil at least 75w90 and 75w110 if you are towing hard.

Vent tube plugged or problems in diff.

Pinion bearings discolored. Been hot. Replaced pinion and carrier bearings.
Should be good to go.

Pinion bearings discolored from heat. Replaced pinion and carrier bearings. Should be good to go.

So did you determan a cause for the oil getting hot?

Pinion bearings were discolored from heat.
 

Replaced pinion and carrier bearings. Should be good to go.

I get that part but, they don't get hot for no reason. Their was a cause that allowed them to get hot.

What is going to prevent them from getting hot again if their was no cause determined?