CONTROL VALVE/OIL PUMP ROTOR & SLIDE-SERVICE SPECS.125/125C
Beginning mid-April, 1983, service parts became available to separately replace the oil pump rotor and slide of the control valve and oil pump assembly on all THM 125C transaxles. The service procedure in this bulletin must be followed to assure proper end clearance of the replacement oil pump rotor and/or slide into the original control valve and oil pump assembly.
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.
I. DISASSEMBLY OF THE OIL PUMP
A. Disassemble the oil pump assembly (Figure 1) following procedures outlined in the Service Information Manual.
II. SELECTING THE PUMP ROTOR AND/OR SLIDE
A. Use a vernier micrometer to measure the original pump rotor and/or slide thickness accurately (Figure 2). Measure on flat, undamaged surfaces to obtain the most accurate reading.
NOTE: The replacement part will provide the same end clearance originally built into the transaxle. The proper end clearance specification is 0.066mm to 0.092mm (0.0026" to 0.0036").
B. Using the original part measurement, order a replacement part using the following selective charts:
1982-1983 THM 125C SELECTIVE PUMP ROTOR (15 TOOTH)
PART NO. 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
1982-1983 THM 125C SELECTIVE PUMP SLIDE
PART NO. 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 replacement rotor and/or slide to remove any burrs, and measure the replacement parts with micrometer to assure the proper selection.
NOTE: 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 the Service Information Manual.
B. After assembling the control valve and oil pump assembly onto the transaxle, check for proper rotor and slide end 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 pressure. Refer to the "Preliminary Check Procedure" in the Service Information Manual for oil pressure specifications.
IV. OTHER OIL PUMP SERVICE PARTS (FIGURE l)
A. Listed below are parts previously released to service the oil pump of the control valve pump assembly.
ILL. NO. PART NAME PART NUMBER --- ---------- -----------
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.
