CONTROL VALVE/OIL PUMP ROTOR & SLIDE-SERVICE SPECS.125/125C
Beginning mid-April 1983, service parts became available to service the oil pump rotor and slide of the control valve and oil pump assembly on all THM 125/125C transaxles. This service procedure must be followed to assure proper end clearance.
SERVICE PROCEDURE
NOTICE: DO NOT attempt to service the oil pump rotor if either the pump pocket or auxiliary valve body/pump cover surfaces are scored. Servicing of the oil pump rotor and slide should be performed ONLY if the selective pump rotor, pump drive shaft, or the pump slide show signs of wear.
1. DISASSEMBLY OF THE OIL PUMP
Disassemble the oil pump (see Figure 1) following procedures outlined in your Service Manual.
SELECTING THE PUMP ROTOR AND/OR SLIDE
A. Use a micrometer to measure the original pump rotor and/or slide thickness accurately (see Figure 2). Measure on flat, undamaged surfaces to obtain the most accurate reading.
B. Using the original part measurement, order a replacement part using the following selective charts:
1980-1981 THM 125 SELECTIVE PUMP ROTOR (20 TOOTH)
PART NUMBER THICKNESS (MM) THICKNESS (IN) ------- --------------- -------------- 8631495 17.943-17.965 0.7065 - 0.7069 8631496 17.956-17.968 0.7070 - 0.7074 8631497 17.969-17.981 0.7075 - 0.7079 8631514 17.982 17.994 0.7080 - 0.7084 8631515 17.995-18.008 0.7085 - 0.7089
NOTICE: The replacement part will provide the same end clearance that the transaxle was originally built with. The proper end clearance specification is 0.066mm to 0.092mm (0.0026" to 0.0036").
1982-1983 THM 125C SELECTIVE PUMP ROTOR (15 TOOTH)
PART NUMBER THICKNESS (MM) THICKNESS (IN) ------- -------------- -------------- 8637768 17.917 - 17.929 0.7055 - 0.7059 8637769 17.930 - 17.942 0.7060 - 0.7064 8637178 17.943 - 17.955 0.7065 - 0.7069 8637179 17.956 - 17.968 0.7070 - 0.7074 8637180 17.969 - 17.981 0.7075 - 0.7079
1980-1983 THM 125/125C SELECTIVE PUMP SLIDE
PART NUMBER THICKNESS (MM) THICKNESS (IN) ------- -------------- -------------- 8631800 17.955-17.967 0.7070 - 0.7074 8631801 17.968-17.980 0.7075 - 0.7079 8631802 17.981-17.993 0.7080 - 0.7084 8631803 17.994-18.006 0.7085 - 0.7089 8631804 18.007-18.020 0.7090 - 0.7094
C. Hone both sides of the replacoment rotor and/or slide to remove any burrs, and measure the replacement parts with micrometer to assure the proper selection.
NOTICE: Incorrect rotor selection could result in a damaged control valve and oil pump assembly, a sheared pump drive shaft and/or low oil pressure. Incorrect slide selection could result in incorrect line pressures.
III.ASSEMBLY
A. Reassemble the oil pump assembly following procedures outlined in your Service Manual.
B. After assembling the control valve and oil pump assembly onto the transaxle, check for proper rotor and slied and clearance by turning the pump drive shaft. The pump rotor should turn freely. If the pump rotor does not turn freely, recheck the pump rotor and/or slide selection.
C. Install the transaxle into the vehicle.
D. Before road testing the vehicle, install an oil pressure gage into the transaxle and check oil pressurs. Refer to the "Preliminary Check Procedures" in your Service Manual for oil pressure specifications.
IV. OTHER OIL PUMP SERVICE PARTS (Refer To Figure l)
Listed below are parts previously released to service the oil pump of the control valve pump assembly.
ILL. PART NUMBER PART NAME NUMBER
18 THM 125 Oil Pump Drive Shaft (1980-1981) 8631869 18 THM 125C Oil Pump Drive Shaft (1982-1983) 8637777 357 Pump Drive Shaft Seal 8637569 354 Pump Drive Shaft Bearing Assembly 8631277 351 Pump Vane Ring 8631279 352 Pump Vane 8631280 346-347 Pump Slide Seal Package 8631947 344 Pump Cover Sleeve 8631288 359 Pump Priming Spring 8631717 345 Slide Pivot Pin 8628273
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.
