NO SERVICE FRONT AXLE ASSY. (REPLACE COMPLETE AXLE ASSY.)

SUBJECT: REPLACING FRONT AXLE PARTS MAY RESULT IN VIBRATION (REPLACE ENTIRE AXLE ASSEMBLY)

MODELS: 1990-93 L-VANS

THIS BULLETIN CANCELS AND REPLACES GMC TRUCK BULLETIN 92-4C-18, DATED OCTOBER 1991. IT IS BEING REVISED TO INCLUDE THE 1993 MODEL YEAR.

CONDITION

Each front axle for 1990-93 L-vans is balanced with the pinion flange assembly modified to act as a harmonic member which reduces audible driveline disturbance.

CAUSE

Replacing the ring and pinion gear set, pinion flange assembly, or the pinion bearings will disturb the balance integrity of the axle and result in a vibration.

CORRECTION

Do not replace either the ring and pinion gear set, pinion flange assembly, or the pinion bearings in a 1990-93 L-van front axle. If replacement of one of these parts is necessary, replace the entire axle assembly, using the system-balanced service axle assemblies listed below.

Prior to replacement of the axle assembly, it is essential that the position of the propeller shaft relative to all of the driveline components be observed and reference marked. When replacing the pinion seal, the pinion yoke must be referenced to the pinion to ensure reassembly in the original position. All components must be reassembled in the same relationship to each other. Attach propeller shaft to replacement axle first, then to the transfer case, and road test. If vibration is noted, re-index propeller shaft to transfer case and test drive again.

SERVICE PARTS INFORMATION

Vehicle Axle Ratio Part Number Description ------- ---------- ----------- ----------- L-Van 3.42 26022779 Service Axle Assembly, Front L-Van 3.73 26022781 Service Axle Assembly, Front

Parts are currently available from GMSPO.

WARRANTY INFORMATION

For vehicles repaired under warranty, use:

Labor Op Labor Time -------- ---------- F2142 See Applicable Labor Time Guide

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.