HIGH EFFORT AND/OR GEAR CLASH NOISE DURING SHIFTING

VEHICLES AFFECTED: 1985-86 'M' Car - Manual Transmission

Some of the subject vehicles may exhibit conditions of high effort and/or gear clash noise during some shifting maneuvers. This condition may be more prevalent during cold weather (below freezing) and also when shifting during initial vehicle warm-up periods.

During 1986 model year, the factory fill for transmission lubricant was changed from 8OW/90 to 75W. This change was made in conjunction with internal component changes described below.

Vehicles built prior to GK719594 (2 door) and GK817385 (4 door) were filled with 8OW/90 oil and should be serviced with the same oil, unless, steps 1-3 are performed.

Vehicles beginning with the above VIN serial numbers were factory filled with 75W transmission oil. When servicing these vehicles 75W or SAE 5W-30 engine oil must be used.

Vehicles built from VIN's GK721183 (2 door) and GK818780 (4 door) onward incorporate other revisions which are designed to minimize the described conditions. At ambient temperatures below -17 degrees Celsius (0 degrees Fahrenheit) some vehicles may still exhibit the described conditions to a lesser degree.

Corrective action for vehicles with these conditions that were built prior to the breakpoint VIN's previously listed are as described in steps 1-5.

1. Replace ring 2nd/3rd gears - use P/N 96055142 (2 pcs.)

2. Replace gear - countershaft - 2nd gear - use P/N 96055162 (1 pc.)

3. Replace gear - countershaft - 3rd - use P/N 96055163 (1 pc.) Install above parts and reassemble transmission using appropriate procedures from the shop manual except for the selection of the input shaft bearing shim size.

4. Having determined the step height per shop manual procedure refer to the shim selection chart for input shaft shim size selection.

Dial Gauge Thickness of Input Shaft Reading (MM) Shim (MM) To Be Installed ------------ -------------------------- 0.48 - 0.52 0.60 0.53 - 0.57 0.60 0.58 - 0.62 0.65 0.63 - 0.67 0.70 0.68 - 0.72 0.75 0.73 - 0.77 0.80 0.78 - 0.82 0.85 0.83 - 0.87 0.90 0.88 - 0.92 0.95 0.93 - 0.97 1.00 0.98 - 1.02 1.05 1.03 - 1.07 1.10

5. Refill transmission with lubricant using SAE 5W-30 engine oil or 75W gear lubricant.

NOTICE: Step 5 is only recommended provided that steps 1-3 are completed. In the event that steps 1-3 are not carried out on the subject transmission, and the vehicle VIN is prior to the breakpoints GK719594 (2 door) and GK817385 (4 door) the lubricant to be used is 8OW/90 per shop manual.

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.