TRANSMISSION PUMP SERVICE THM 440-T4 TRANSMISSION
VEHICLES AFFECTED: All 1984-85 Vehicles Equipped With THM 440-T4 Transmission
Service parts are now available to service the oil pump rotor, slide and vanes in the pump body assembly on all THM 440-T4 transmissions. This service procedure on all THM 440-T4 transmissions must be followed to assure proper end clearance on the oil pump rotor and slide.
SERVICE PROCEDURE:
Notice: Do not attempt to service the oil pump rotor, if either the pump body pocket or pump body cover surfaces are scored. Servicing of the oil pump rotor, slide, and vanes should be performed only if the selective pump rotor, slide or the vanes show wear.
1. Disassembly of the oil pump:
a. Disassemble the oil pump assembly following procedures outlined in the Service Manual. Refer to Figure 1 for the THM 440-T4 transmission oil pump assembly.
2. Selecting the pump rotor, slide and vanes:
a. Use a micrometer to measure the original pump rotor, slide, and vane thickness accurately (Figure 2). To obtain the most accurate reading, measure on flat, undamaged surfaces.
b. Using the original part measurement, order replacement parts according to selective charts A, B or C.
c. Hone both sides of the replacement rotor, vanes, and slide to remove any burrs and measure the replacement parts with a micrometer to assure proper selection. Incorrect rotor selection could result in a damaged oil pump aseembly, and/or low oil pressure. Incorrect slide selection could result in incorrect line pressure.
3. Service Parts Information:
The rotor and vane are serviced separately. The slide is serviced in a service package which includes the following parts:
Oil seal ring (slide to cover) (207) 'O' ring seal (slide seal backup) (208) pump slide seal (212) pump slide seal support (213)
Notice: The replacement part will provide the same clearance that the oil pump assembly was originally built with. The proper end clearance specification is .0635mm to .0813mm (.0025 in. to .0032 in.) for the rotor and vanes and .0330mm to .0559mm (.0013 in. to .0022 in.) for the slide.
Due to the factory selection of the oil seal ring (207), any field substitution of these parts will result in transaxle damage or could cause pump failure. These parts are serviceable only in the slide package (Chart B).
The pump slide seal (212) and the pump slide seal support (213) can be serviced by ordering package 8646916. These parts are not selective.
4. Assembly:
a. Reassemble the oil pump assembly following procedures outlined in the service Manual.
b. After assembling the oil pump, install the pump shaft and check for proper rotor and slide clearance by turning the pump shaft. The pump shaft should turn freely. If the pump shaft does not turn freely, recheck the pump rotor and slide selection.
c. Install the transmission into the vehicle.
d. Before road testing the vehicle, install an oil pressure gauge to the transmission and check oil pressure. Refer to the Service Manual for oil pressure specifications.
ROTOR, VANE, SLIDE SELECTIVE CHARTS
CHART A - Selective Pump Rotor
PART NUMBER THICKNESS IN mm THICKNESS IN INCHES ----------- --------------- ------------------- 8656267 17.953 - 17.963 .7068 - .7072 865628 17.963 - 17.973 .7072 - .7076 6656269 17.973 - 17.983 .7076 - .7080 8656270 17.983 - 17.993 .7060 - .7084 6656271 17.993 - 18.003 .7084 - .7088
CHART B - Selective Pump Slide, and Seals
PART NUMBER THICKNESS IN mm THICKNESS IN INCHES ----------- ----------------- -------------------- 8646911 17.983 - 17.993 .7080 - .7084 8646912 17.993 - 18.003 .7084 - .7088 8646913 18.003 - 18.013 .7088 - .7092 8646914 18.013 - 18.023 .7092 - .7096 8646915 18.023 - 18.033 .7096 - .7100
CHART C - Selective Pump Vane
PART NUMBER THICKNESS IN mm THICKNESS IN INCHES ----------- --------------- -------------------- 8644661 17.943 - 17.961 .7064 - .7071 6644662 17.961 - 17.979 .7071 - .7078 8644663 17.979 - 17.997 .7078 - .7085
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.
