puting a drain plug on the rear end

I swap my truck's rear out at 25k intervals. I drive the mav a bit harder and swap at various intervals, maybe 10k.

Also, I may be mistaken, but doesn't some of that oil make it to the axle bearings in the tubes? Not sure, I never pulled the axles with the oil still in the diff.

 

Yes..that is how the bearings get their lube. There's an axle seal at the end of the tube.

This is true with a transmission...but you can't rake gears in a rear end.

It is 90W...or close to it. It don't get as hot as engine oil.

 

i personaly have the drain because i swap my third members out for different ratio ones depending on if i want to goto the drag strip or drive on the street. its nice to have the oil completly drain out the bottom if the housing and not spray all over when you crack the seal of the thirdmember to the housing. it also drains that last inch of oil that gets traped in there if you dont have the drain hole. we do recomend that the oil gets changed between 20k and 40k. oil does break down. a diff can get up to 180 degrees after a good long drive. different oils have different abilitys to provide protection under different conditions so its important to run a good quality oil.

 

I kind of think that way. My 71 F100 had around 275K miles on the original 9" before the center chunk was ever pulled. Gears and bearings were fine.
I did add a drain plug though. I don't think I will change the fluid very often if at all though. Heck I change the dang center chunk for a ratio change so often I never need to drain it just for new gear oil lol
Thinking about going back to a 3.0 from a 3.25 now. lol
clint

 

the oil doe's go bad if you ever changed some after a few years it STINKS bad and it turns black like old motor oil

i was thinking that i can drill a whole in the bottom and weld a nut then put a bolt in it witch cost $2 and a gasket cost 4 to 5 bucks and it will pay off when you change the oil later and it only takes 5 min to do so then 1 hour

 

the problem with using a drain plug that is a bolt with gasket is that it will need a pefectly flat surface to seal to. if you put the nut on the out side your asking for it to get knocked off from hiting something or be jacked up on. if you weld it on the inside you will find that the housing surface is not flat and smooth on the bottom.

 

I agree. That is why drilling and tapping into the bottom an using a pipe-threaded plug is perfect. If you use a recessed allen plug, it will have 2-3 threads to grab on to in the bottom, and will be flush to the bottom of the diff when it is screwed in.

Mine has worked fine for 4 years, doesn't drip a bit, and only needs a couple wraps of teflon to keep it in and dry.

 

The allen plug is a good idea. I was able to weld a nut inside. My surface IS flat and smooth. I did the nut because I thought the housing was too thin to try threading AND I didn't want the head of the bolt getting hit, so I put the ring around it. Looks like something that could have been done factory.