SERVICE MANUAL UPDATE SEC. 3A1 4-WHEEL ALIGNMENT REVISED. GMC Truck Jimmy

SUBJECT: 4 WHEEL ALIGNMENT/FRAME BRACKET KNOCKOUT TOOL (SERVICE MANUAL UPDATE X9130 SECTION 3A-1

MODELS: 1990-91 L VANS

All 1990 and 1991 all-wheel drive L vans are sensitive to wheel compensation procedures when using Hunter 4-wheel computerized alignment equipment. Hunter C, D, F, G, H, and J111 models will not tolerate the movement of more than one head at a time during the compensation procedure and also require that all heads remain vertical to obtain correct readings.

These requirements cannot be satisfied because of the viscous clutch in the Borg Warner 4472 transfer case. The result of these incorrect readings will be inaccurate toe settings that could generate customer complaints.

Owners of these types of alignment machines can resolve this condition with the installation of revised Hunter computer software. This software is available through Hunter Engineering Company. Telephone (314) 731-3020 or contact your local Hunter service representative for details.

Dealers who own other brands of alignment equipment should check with their manufacturer's representative to ensure that their equipment is not similarly affected.

KNOCKOUT TOOL

Tool #J38794, used for C/K truck frame bracket knockout removal, is also used for L vans. See Dealer Service Information Letter DS-90-25, which includes proper procedure for use of removal tool and new alignment set specifications for the L van.

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.