The Stovebolt Site Forums The Parking Lot Big Bolts Pinion Gear lubrication

My 49 6400 truck has a two speed differential and is running well. When I first got the truck two years ago I checked and topped off the differential fluid. Today I noticed that the pinion gear housing has a fill plug. I checked and there is fluid in the housing. Following disassembly and in the reassembly process the shop manual says to add 1 pint of gear oil to the pinion gear housing. I have never had the differential apart and in only looking at the drawings in the shop manual, doesn't the gear oil from the differential flow into the pinion gear housing thru the bearings. The book never mentions checking the fluid level or gives a level to maintain in the pinion gear housing, so that is why I question the need to add any fluid to the pinion gear housing if you have never had the unit disassemled. Am I correct in my assumption that keeping the gear oil at the proper level in the differential will properly provide lubricant to the pinion gear housing?

Jim

The fill plug on top of the pinion housing is for adding fluid to the pinion bearings only after extended storage , to insure the truck was not loaded and run under a heavy load without lubricant distributed through the bearings.
I think it is not necessary to do this and it will "overfill" the differential.......requiring you to drain some out after the initial run (after L O N G storage, rebuild; that's another subject).

i agree. if you think the gears are dry, you might jack the rear wheel off the ground and spin the wheels. as long as the driveshaft is turning, so are the gears. this ought to get enough lube to the gears and bearings.

Thanks for the replies. I don't have any leaks in the system and I know there is lube in the pinion housing so I'll just check the differential level from time to time. Thanks again.
Jim

I believe it's just after "service" to make sure you aren't running it dry on startup. After that, the oil gets splashed there while driving. This is also how tractors oil the Tork-amplifiers and other things when serviced. Eventually oil gets there, but runs slowly in doing it.