Front Axle Fluid Leak (Inspect for Kinked Axle Vent Tube). GMC Truck Sierra

Subject:

Front Axle Fluid Leak (Inspect for Kinked Axle Vent Tube)

Models:

2007-2008 Chevrolet Silverado 2500 and 3500 Series

2007-2008 GMC Sierra 2500 and 3500 Series

with 4WD

Condition

Some customers may comment that the front axle is leaking fluid. This condition may occur after the vehicle has operated in 4WD mode long enough for the front axle to be thoroughly warmed up; generally for 16 or more kilometers (10 or more miles).

A visual inspection may reveal that the fluid is leaking from the pinion shaft oil seal, output shaft seals, or carrier assembly case halves.

Cause

The cause of this condition may be due a kinked axle vent tube. This restriction could result in pressure building up inside the axle and forcing fluid out past the seals.

Correction

Note: This is the same condition that is covered in Service Update #07286 that was issued for vehicles in dealer inventory. This information is provided to cover sold vehicles.

Prior to vehicle assembly, the axle vent tube is folded over and secured with tape to prevent axle fluid leakage during shipping. On some of these vehicles, the tape may not have been removed during vehicle assembly. Remove the tape from the vent tube and then unfold the vent tube to ensure proper vent operation. Use the procedure listed below.

Open the hood.


(1)	Front Differential Vent Tube
(2)	Underhood Electrical Center
(3)	Battery Tray
(4)	Radiator Hose

Locate the front differential vent tube (1). The vent tube (1) is located between the battery tray (3) and the underhood electrical center (2).

Inspect the front differential vent tube.

•	If the front differential vent tube is kinked or folded over and taped (1B), remove the tape from the wiring bundle and then unfold the vent tube to ensure proper vent tube operation. Proceed to step 4.

•	If the front differential vent tube is NOT kinked or folded over and taped (1A), refer to Front Axle Lubricant Leak Diagnosis in SI and repair as needed.

After unfolding the vent tube, the seals should no longer leak because the axle no longer becomes pressurized during use. Verify that the axle will not leak by cleaning the axle and surrounding area of any fluid residual. Inspect the fluid level and add as needed. Road test the vehicle in Auto 4WD or 4WD mode for at least 16 km (10 miles). If a leak is observed after the road test, refer to Front Axle Lubricant Leak Diagnosis in SI and repair as needed.

Warranty Information

For vehicles repaired under warranty, use:

Labor Operation	Description	Labor Time
F9713*	Inspect Front Axle Vent Tube	0.2 hr
Add	To Remove Kink, Clean Axle, Check Level, Road Test Vehicle and Recheck Axle for Leaks	0.7 hr
* This labor operation number is for bulletin use only. This number will not be published in the Labor Time Guide.