GEAR SHIFT LEVER RATTLE IN FORWARD GEARS

Model and Year 1988 C/K TRUCKS WITH HM-290 MANUAL TRANSMISSION

This bulletin covers 1988 C/K Trucks equipped with a HM-29o 4 or 5 speed manual transmission which may experience noises in any or all forward gears, or a condition of shift lever rattle/buzz and/or excessive vibration of the shift lever (Figure 1) . Some movement of the shift lever is normal, especially with the 4.3L engine, unless it causes a rattling noise. Any of the above conditions could be caused by excessive clearance in the shift lever housing assembly transmitting vibration and rattle to the driver compartment. The condition(s) will increase with engine RPM and be in any or all gears, including neutral. Conditions explained as shift lever rattle/buzz and excess vibration of the shifter can be repaired by installing a new shift lever housing assembly: The new shift lever housing assembly uses compression grommets at the pivot points, eliminating the chance of excess clearances due to improper shim selection.

IMPORTANT: A slight gear rattle at low engine RPM (800-1200 RPM) is normal to all manual transmissions. The service repair described above will only reduce the rattle condition due to improper shimming.

DATE OF PRODUCTION CHANGE: (Figure 2)

Beginning May 20, 1988 all HM-290 transmissions are built with a new shift lever housing assembly that requires no shims. This new part uses an updated material for the boot and inside lever seal so no o-rings (129) and (131) are required to prevent leakage.

NOTE : There was an interim change January 5, 1988 to May 20, 1988 where the updated boot and inside seal material were used (on the previous part with shims) so no o-rings were required.

SERVICE ACTION:

To repair this condition, replace the shift lever housing assembly with the parts listed under service Parts Information.

SERVICE PARTS INFORMATION:

Part No. Description -------- -----------

23049538 Housing Assembly, Shift Lever (RPO MCO) (4-speed) 08672191 Housing Assembly, Shift Lever (RPO MG5) (5-speed) 23049572 Seal (service only)

SERVICE MANUAL REFERENCE:

Refer to the On-Vehicle Service Section 7B of the 1988 C/K Pick-up Truck service manual for service procedures.

LABOR TIME INFORMATION:

Labor Operation: K1120 Labor Time C/K Truck: .7 Hr.

SERVICE NOTES:

The HM-290 overhaul video shows the axial clearance measurement of the shift lever housing that requires shims. This checking procedure is not for the new shift lever housing that uses the compression grommets instead of shims.

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.