TRANSFER CASE HOPS OUT OF 4-HIGH, OR NO DRIVE IN 2 & 4

SUBJECT: TRANSFER CASE HOPS OUT OF 4-HIGH, OR NO DRIVE IN 2 OR 4-HIGH RANGES AND/OR GRINDING NOISE (INSTALL MAINSHAFT/RANGE HUB KIT)

MODELS: 1989-96 CHEVROLET AND GMC K3 MODELS WITH BORG-WARNER 1370, 4401 OR 4470 TRANSFER CASE

CONDITION:

SOME OWNERS MAY REPORT THE TRANSFER CASE HOPS OUT OF 4 HIGH RANGE OR, NO DRIVE IN 2 OR 4 HIGH RANGES AND/OR MAKES A GRINDING NOISE.

CAUSE:

MARGINAL LUBRICATION OF THE RANGE FORK. AN ADDITIONAL CAUSE IN THE 4470 MODEL TRANSFER CASE MAY BE A DAMAGED OIL PUMP ASSEMBLY.

CORRECTION:

INSTALL A REVISED MAIN SHAFT/RANGE HUB ASSEMBLY (SHAFT KIT). THE REVISED MAIN SHAFT IS DRILLED TO PROVIDE PRESSURIZED OIL TO THE RANGE FORK/RANGE HUB AREA AND, THE RANGE HUB HAS HAD TWO OPPOSING INTERNAL SPLINES REMOVED TO PROVIDE A PATH FOR PRESSURIZED OIL FLOW TO THE RANGE FORK. IF THE RANGE FORK SHOWS SIGNS OF WEAR, IT SHOULD ALSO BE REPLACED.

NOTICE: WHEN ASSEMBLING THE RANGE HUB TO THE MAIN SHAFT, BE CERTAIN TO ALIGN THE OIL HOLE IN THE SHAFT WITH ONE OF THE MISSING SPLINE SLOTS IN THE RANGE HUB (FIGURE 2). IMPROPER ALIGNMENT MAY RESULT IN EARLY FORK WEAR-OUT.

INSPECT THE OIL PUMP ON 4470 MODEL TRANSFER CASES. THIS PUMP IS DRIVEN BY THE MAIN SHAFT USING A FLAT. THE PUMP SHOULD BE INSPECTED FOR THE PRESENCE OF THIS FLAT (FIGURE 1). IF THIS FLAT IS MISSING, THE PUMP SHOULD BE REPLACED.

SERVICE PROCEDURE:

FOR TRANSFER CASE REMOVAL AND REPLACEMENT PROCEDURE REFER TO THE APPROPRIATE C/K SERVICE MANUAL, SECTION 7D, TRANSFER CASE REPLACEMENT. REFER TO THE APPROPRIATE LIGHT DUTY TRUCK UNIT REPAIR MANUAL FOR SHIFT DETENT LEVER ADJUSTMENT.

THE FOLLOWING PARTS MUST BE REPLACED WHEN REPAIRING THE TRANSFER CASE: -SPEEDOMETER TONE WHEEL -YOKE NUT (FIXED YOKE MODELS ONLY) -SPLINE SEAL (FIXED YOKE MODELS ONLY)

PARTS INFORMATION

P/N DESCRIPTION QTY 12387973 SHAFT KIT (1370/4401 W/FIXED YOKE) 1 12387974 SHAFT KIT (1370/4401 W/SLIP YOKE) 1 12387975 SHAFT KIT (4470 W/FIXED YOKE) 1 12375241 SHAFT KIT (4470 W/SLIP YOKE) 1 12386677 OIL PUMP (4470) 1 15619384 RANGE SHIFT FORK (ALL) 1 15619401 YOKE NUT (ALL FIXED YOKE) 1 15635532 SPLINE SEAL (ALL FIXED YOKE) 1 15580305 TONE WHEEL (1370/4401) 1 15619399 TONE WHEEL (4470) 1

PARTS ARE CURRENTLY AVAILABLE FROM GMSPO.

WARRANTY INFORMATION

FOR VEHICLES REPAIRED UNDER WARRANTY, USE:

LABOR OP DESCRIPTION LABOR TIME K4400 TRANSFER CASE USE PUBLISHED ASSEMBLY - RECONDITION LABOR OPERATION TIME

IMPORTANT: LABOR OPERATION IS CODED TO BASE VEHICLE COVERAGE IN THE WARRANTY SYSTEM.

FIGURES: 3

CAPTIONS: FIGURE 1 - MODEL 4470 OIL PUMP ASSEMBLY FIGURE 2 - MAIN SHAFT AND HUB FIGURE 3 - BORG-WARNER TRANSFER CASE IDENTIFICATION

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.

COPYRIGHT 1996 GENERAL MOTORS CORPORATION. ALL RIGHTS RESERVED.