PUMP WHINE OR MOAN NOISE NEW PUMP DESIGN/THM 700-R4
MODEL AND YEAR: 1985-87 PASSENGER CARS AND TRUCKS WITH THM 700-R4 TRANSMISSIONS
A whine or moan on a 1985 through 1987 THM 700-R4 transmission may be caused by line pressure instability in a seven-vage pump. A ten-vane pump, to provide stable line pressure, is now used on all 1987 THM 700-R4 models and available to service 1985 and early 1987 model transmissions.
Ten-vane pumps for all 1987 THM 700-R4 production and service Replacement Transmission Assembly (SRTA) models have been used since October 28, 1986 (Julian date 301). Refer to Figure 1.
When using the ten-vane pump body assembly to service a THM 700-R4 transmiss- ion for correction of a whine or moan condition, mate the new pump body to the pump cover taken from the transmissions existing oil pump (Refer Figure 2).
PARTS INFORMATION
PART NAME PART NUMBER --------- ----------- Pump Body Assembly 8649964 (10 vane)
NOTE: Due to a pump cover casting change in 1985, a 1982 through 1984 THM 700-R4 transmission must be serviced using a complete pump assembly. Service parts for these earlier model years will be available at a later date.
Seven-vane pump body assemblies, part number 8649950, should be used to service 1985 through 1986 THM 700-R4 transmissions until current service stock is depleted. The ten-vane pump body assemblies should be used for any 19 8 5 through 1986 model exhibiting a whine or moan condition and all 1987 THM 700-R4 transmission models.
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.
