So check this one out. I changed the oil in my diff about 1,800 miles ago. I replaced the oil with the EXACT same brand, weight, quantity, and slip additive as was previously in there. But now, ever since I did the oil change, I have two odd conditions occurring. I have gear oil coming out the the vent tube. Enough to drip on the ground when parked. I also have a leak at the driveshaft. But this leak is not coming from around the pinion seal against the axle housing. It's actually leaking from the front of the pinion, like around the shaft that's covered by the driveshaft. The leak is physically coming from between the drive shaft joint and the face of the pinion piece that the universal joint bolts to.

WTF??? Any thoughts on these or what would cause these two conditions to occur right after a gear oil change? I have checked the level/quantity twice now and no problems. When I check the level, there doesn't appear to be any foaming or anything goofy going on. There's also no discoloration or new contaminants in the gear oil following the oil change either. I'm at a loss on this one, but it's annoying.

 

You may have a bad axle bearing or diff bearing heating up the gear fluid and causing the leaks. With big off road tires you can't always hear a bearing when it goes bad.

 

Isn't it too coincidental that this started with an oil change though? And define heating up; how hot is too hot to cause these symptoms with the fluid?

 

The fluid change shouldn't have anything to do with it if you used the correct amount and the correct fluid. I think I would pick up an infrared thermometer. I bought one at Autozone. And check the temperatures of the axle housing at the bearings and the diff at the bearings to see what I could find out.

 

Yea, I'll do that. Or next long drive I'll at least feel for any hot spots or uneven temps.

 

I was trying to find a bad bearing and I noticed my differential was fairly hot to the touch at the pinion bearing. I found out that it was normal. My bad bearing was the RF bearing hub. It had me baffled because when I turned left which added load the noise stopped and when I turned right decreasing the load on the wheel, it got louder. Usually that means the LF bearing hub is bad. Kept me confused for a while.

 

I have no noise problems.

 

I'd assume the vent isn't clogged if it's leaking too.... strange for sure

 

Yea Pat, that's been my initial thought all along also. Pressure build up for some reason. I don't get it, nor what's different.

I drove 60+ miles today, mostly freeway. Stopped and immediately checked the housing. The axle tube where the bearings are (outer at the wheels and inner just by the center housing) were both cool to the touch and no variation in temp (e.g. One side warmer than the other). The pinion/front area of the center was very warm, but not what I would call hot. I could leave my hand on it. The rear cover where all the fluid would be was cooler than the front pinion area. I don't know what's considered 'normal' for an axle temp, but there was nothing indicating a problem or temp problem.

????????

 

For the record, what gear oil did you put in the diff and how much?

 

Amsoil Severe Gear 75W140. 5 Quarts.

Now...before you lose your mind...I have a Mag Hytec diff cover that's been on the truck since ~500 miles (I bought this truck new and installed it myself). The diff cover has a dipstick with a low and high mark as specified by Mag Hytec and their recommended capacity. 5 quarts puts the level right dead center of the two marks; just like checking your engine oil.

Also...as already stated...this is the same oil and same quantity that's been in this truck for 180,000 miles. This is the third time the oil has been changed...with the same brand, weight, and quantity. And this is the first time I've ever had this issue. I'm sure I've overlooked something, but not a clue what it is.

 

That's interesting. If I remember correctly with the stock cover, it only holds 2.6 qts.

 

I went and got new hose to change out the vent line and maybe take a 1/2 quart out just to try something. I just remembered I did replace all the brake lines when I did a brake job at the same time. I had that manifold apart where the brake lines and vent all attach, so maybe there's something funny going on there. This ines certainly got me at a loss.

It's getting worse too...more dripping!

 

So removed the vent line today. As expected, completely clear; no restrictions. Also checked by blowing into the axle with the fill cap removed; completely free flowing. So there seems to be no restrictions for air flow or pressure build up in the housing. I replaced the vent hose anyways since I stopped and bought some new. Level is still right where it's always been, so I don't have a clue what's going on.

I was going to remove a 1/2 quart or so just to see what happens, but the old sucking through a hose to create a vacuum effect doesn't work so hot on cold 75W140, hahahahhahaha. May try again later.

I've got a 60 mile drive in the morning so we'll see what happens tomorrow. If I have it coming out the vent again tomorrow I'll reduce the quantity. Really don't know what else to try.

 

How much further up on the rear end is the new fill, in relation to the factory fill line?

Can't imagine a cover alone holding 2qts more?

Any chance you got a (big) exhaust leak just in front of the axle heating things up?



How did the previous fluid look? And the magnet?
Any indication of bearing failure/excessive wear?