Hi every one,,I have a F53 chassis motorhome 45000 miles and I noticed my rear end, Dana 80 5:38 was making a whining noise while pulling and the noise would go away while coasting,,so I had my mechanic replace the carrier bearings and the pinion bearing, but not the pinion bearing race as it looked great. the pinion bearings were loose and some pitting and that socalled lifetime rear end oil (75-90 synthetic) was dark and possibly burned,,well to make a short story longer,, it still seems to whine and when I feel the third memeber around that pinion gear it's hot and the rest of the third member is relatively cool. is the heat thing normal? any ideas? also the ring hear and pinion gears looked fine,, no sign of wear or misalignment...

 

The pinion bearings are the smallest of all 4 bearings so they will be the hottest.
How hot is entirely another matter.
Have you used a infard temp gun to see just how hot it is getting?
Some of the later ford truck with D80s have a aluminum finned cover on them. I even think they hole more lube. If yours doesn't have one you could install one with more lube and fins they could help it run cooler.
How much weight are you moving?

I know a guy who had a problem with rear axles dieing in his trash vacume truck. He spent his driving in figure 8s all night long.
We had a plan to install a small Power steering pump (With out the pressure valveing) on the frame and run it off the drive shaft to a cooler and then to lines hooked to back of the cover. the engine in the truck died and he ended up junking the truck.
(I have seen this sort of thing on Nascar cars years ago)
THis is an idea you might be able to use.

 

I'm pushing about 15000 lbs,and the rig came with the finned back plate,,i do have a infrared temp gauge and i plan to run the vehicle around a bit and see what the temps are,, thanks

 

your problem is the pinion bearing , if the bearing is worn then so is the race ! never replace one with out the other they both wear at the same rate ! as for the oil go back to regular gear oil !

 

Yes I agree,,the race is suspect and I did get rid of the "lifetime" synthetic gear oil and went with a quality 75w90 regular oil,,,,