FRT. DRIVE AXLE LEAKS (INSTALL REVISED SEALS & AXLE VENT)

SUBJECT: FRONT DRIVE AXLE LEAKS

MODELS: 1988-92 Kl, K2 (7,200# GVWR OR LESS) TRUCKS

Some owners of 1988-92 Kl, K2 (7,200# GVWR or less) vehicles may comment that their vehicle experiences leaks from the front axle. These leaks may come from three areas:

1. The differential output shaft seals (Figure 1). These leaks may be caused by the outer seal lip riding too far outboard on the axle flange radius, resulting in damage to the seal. The leaks may be corrected by replacing the differential output shaft seals with revised seals (P/N 26031569). The seals have the sealing lips moved inboard 5mm (0.2 in.) to prevent contact with the axle flange radius.

2. The mating area between the axle tube and the differential housing (Figure 1). These leaks may be caused by flexing of the axle assembly which fractures the sealing material. The leaks may be corrected by cleaning and resealing the axle tube and differential housing mating area, using the RTV Sealant listed under Service Parts Information.

3. The vent hose connector. These leaks may be caused by inadequate sealer applied to the vent connector threads and relaxation of the vent connector material. The leaks may be corrected by replacing the vent hose connector with a revised connector featuring an 0-ring seal. Refer to GMC Truck Service Bulletin 91-4C-163, dated November 1991 for complete details.

SERVICE PROCEDURE DIFFERENTIAL SHAFT OUTPUT SEALS: ------------------------------- Refer to 1992 Sierra Service Manual (X-9231) Section 4C "SHAFT AND AXLE TUBE ASSEMBLY REPLACEMENT" for the right-hand seal and Section 4C "OUTPUT SHAFT REPLACEMENT" for the left-hand seal. Replace the seals with the redesigned seals (P/N 26031569).

RESEALING OF THE AXLE TUBE TO THE DIFFERENTIAL CASE: ----------------------------- Refer to 1992 Sierra Service Manual (X-9231) Section 4C "SHAFT AND AXLE TUBE ASSEMBLY REPLACEMENT" for removal and replacement procedures. Do NOT use the sealant mentioned in the Service Manual, use RTV Silicone (P/N 12345739) instead.

NOTICE: Care should be used when cleaning the mating surfaces to prevent gouging or damaging the surfaces.

VENT HOSE CONNECTOR:

Refer to GMC Truck Service Bulletin 91-4C-163, dated November 1991 for parts information and the installation procedure.

SERVICE PARTS INFORMATION

Part Number Description Qty/Veh. ------ ----------- ------- 26031569 Seal, Front Drive Axle 2 12345739 Sealant, RTV Silicone (3.35 As Reqd. or oz. Tube) 123459971 Sealant, RTV Silicone (10.0 As Reqd. oz. Cart.)

Parts are expected to be available on 6/8/92. In case of limited inventory, parts will be placed on 400 control to waive VIP surcharges. Only verifi- able emergency orders will be accepted. GMSPO will make every effort to obtain parts. However, the part will be shipped premium transportation at the dealer's expense and all other order types will be placed on backorder until the 400 control is removed.

WARRANTY INFORMATION

For vehicles repaired under warranty:

Refer to the appropriate Labor Time Guide for Labor Operations and Labor Times.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.