The Stovebolt Site Forums The Shop Area General Truck Talk Draining differential

I was under my 46 1/2 ton this weekend looking at the differential and realized there was no bolt or fitting on the bottom to drain the oil. I have the shop manual & real axel overhal manual, but neither mention how to drain the oil. Was it designed that you removed the back cover to drain? Or is the lower torque tube lock nut supposed to be used as the drain hole. Sorry for the newbie question (I tried the search function first). Thanks.

You can drain it by removing the bottom bolt on the cover, but it's best to remove the cover to ensire that all the old oil is drained as well as being an opportunity to inspect the the internals of the diff.

You have to pop the cover - a drain plug would be nice.

Thanks much! - for a while there I thought my eyes were getting way worse that I couldn't find the drain plug. Thanks for the confirmation.

I agree with Longbox. Removing one of the lower bolts will allow the fluid to drain. You should remove the filler plug to let aur in and speed up the process.

The bottom bolt. It will need some kind of gasket or seal and some suggest a soft copper crush-washer, else it might drip.

I recently did the '58 to '62 1/2 ton punkin' replacement on my '41 3/4 ton that Kip did on his '41. Worked out well and I almost drilled and tapped a 1/2 inch pipe plug in the bottom. When you use the bolt to drain you leave at least a cup of oil behind, also, that would be where any metal particles would end up and it is hard to remove that oil and clean it out well. Alas, I didn't do it cause it was cold and damp and I didn't have a plug....any way it is back together and I am going to be happy with the 3.90 gears.

quick lube places have a nifty suction rig to clean/change differential and trans, once in a while visit doesn't cost much

Bill