Rear Differential Vent Tube Blowing Oil.

Fuddrucker · September 29, 2003

Has anyone ever had this happen? The other day I noticed something leaking under my truk, and discovered that the rear differential fluid had been blowing out of the vent tube. It has never done this before. The only thing I could think of was that I was doing 95mph on the freeway (fastest I had ever done before that was about 85 in this truck) and the oil was getting thrown up into the tube because of the speed the gears were spinning.

I know that when I installed my new Mag-Hytec differential cover, the instructions said the following...

"The vent tube exit on the GM 14-10.5, 14-9.5, 10-8.5 is located on the outside of the carrier bearing in a groove. When the oil gets up in the axle tube the bearing acts like a pump and in some cases will push oil out of the vent tube. It is very important to have oil in the axle tube. Low level should be the inside bottom of axle tube, high should be the bottom of axle. These levels are marked on the dip stick. This insures oil to the wheel bearings and wheel seals also adds more oil to the gear box which extends the life of the differential. There is two ways to fix this problem. The easy way is to get a new hose and route it safely up as high as possible and let the end hang down about 6 in. (over the gas fill tube) About 4 to 6 in. from the top install a in line gas filter. This will let you run the oil in the high range. If it should still be a problem drain out about 1/2 quart and try that if it is ok you have fixed it.

The best fix is to relocate the vent tube to the top of the axle tube about 6 to 10 in. out from the stock location. Drill a 7/16 DIA hole and tape it with a 1/4 pipe tape. Install a Steel Hose Nipple1/4 pipe Thread with a 5/16 barred house end. You can do it your self or it should be done by a good shop. This is the way Dana and Ford builds there axles and they have had no blow by trouble."

I know it sounds like I just answered my own question, but I want to know if this has happened to anyone with the stock differential cover.

Thanks!

Mega Dogmeat · September 30, 2003

I didn't even realize my 10 bolt had a "vent tube"

I don't suppose you have a picture of what it's supposed to look like?

I know that when I swapped my diff fluid about 2 months ago, I filled it a "little" too full I guess, but I never saw where it blew any out a "vent tube"?