Rear diff somehow never needs fluid, but always leaks!?!?!

[1996BLKBauer]

So today, I am doing a few pre-roadtrip checks on my truck, and one of them is to top off the rear diff fluid, I know it leaks form the pinion seal, I am replacing it in a few weeks, but I know the diff is loosing fluid, but the last 2 times I go and fill it, fluid just pours out of the fill hole, like I over filled it previously, so what is going on here? I am losing fluid, but it never id below the fill hole for me to add more... I am confused and concerned.

The truck,

1996 Frod Explorer Eddie Bauer V8 AWD, limited slip diff

My Daily Driver, so no off roading, or racing, or anything crazy like that...

 

[jremington59]

It's probably just not leaking badly. Is there a puddle under it or just wet at the pinion?

 

[1996BLKBauer]

It's probably just not leaking badly. Is there a puddle under it or just wet at the pinion?

The diff, and areas around the pinion are wet, if it sits for a few days there can be a small puddle. Although it can sit for only a few hours and have a puddle, so it is very inconsistent.

 

[bill06447]

The seal probably leaks because the diff is overfilled. The proper "full" level should be about a half inch below the plug.

Bill

 

[koda2000]

petroleum products also expand with heat. make sure the vent line isn't clogged as that can cause the seal to leak due to increased pressure. where i live mud wasps will plug up any hose/hole they find.

 

[imp]

The seal probably leaks because the diff is overfilled. The proper "full" level should be about a half inch below the plug.

Bill

The pinion gear and it's seal sit at the very lowest point in the pumpkin, bathed constantly in oil. Overfill therefore has no effect on the leak, right? imp

 

[RomeovilleIL]

make sure you are on level ground when removing the fill plug. If the rear of the truck is on a jack the differential will be tilted forward. It is possible to overfill by adding fluid from the ABS sensor on top, but you dont encounter that too often.

 

[deweyville65]

The pinion gear and it's seal sit at the very lowest point in the pumpkin, bathed constantly in oil. Overfill therefore has no effect on the leak, right? imp

My thought is that overfill in of itself would not have a effect on the seal leaking. But if the vent is plugged with foreign matter, then driving will heat the oil thereby causing the pressure to vent at the weakest point. Quite possibly the pinion seal. If when the fill plug is removed, and oil runs out, it has to be overfilled. If it were mine, I would pull the fill plug and let the oil drain till it quits running. I have always filled to the bottom of the fill plug, then when checking, if I can reach the oil with my little finger,not worry about it unless I have a leak somewhere, usually an axle seal.

 

[koda2000]

i had another thought, although i'm not sure if this would happen this way. if you drive in deep water and/or you vent tube is off, you could get water in the diff. water, being heavier than oil, would settle on the bottom of the diff with the oil floating on top of the water. if you then remove the fill plug, oil would spill out and you would think the diff was overfilled.

the reason i think this might not happen this way is because a most of time the oil and water will try to mix and end up looking like chocolate milk.

 

[1996BLKBauer]

I think it had to do with heat, I checked it this morning and it need some, My truck never sees off road, or even deep puddles, so I doubt there is any water in there, the vent tube is clear, and is up on the frame like it should be. I did drive it about 2 hours before I started to work on it, and it was 95 degrees yesterday, so it must have been hot still.

In a week or two I will be putting in a new pinion seal, and replacing the U-Joints, so any issue I am having will be done. The U-Joints are just for piece of mind really, since I have no idea when, or if they where ever replaced. Thanks guys for all the input, Tomorrow I am off to Indy to pick up my buddy and have some fun, We are going to KOTS up at Dragstrip in Union Grove, Wi on Saturday, if you are near you should come on out.