A/T - THM 700-R4 Pump Whine or Moan
GMC NUMBER: 87-T-32
SECTION: 7A - Automatic Transmission
DATE: February, 1987
SUBJECT: PUMP WHINE OR MOAN NEW TEN-VANE PUMP DESIGN
MODELS: 1985-87 LIGHT DUTY MODELS WITH THM 700-R4 AUTOMATIC TRANSMISSIONS
(MD8)
Whine or moan on a 1985 through 1987 (before 1986, Julian date 301) THM 700-R4 transmission may be caused by line pressure instability in a seven-vane pump design. A ten-vane pump design to provide stable line pressure is now used on all 1987 THM 700-R4 models and available to service a 1985 through 1987 model transmission.
Figure No. 1 - Transmission Identification:
DATE OF CHANGE (Figure No. 1)
October 28, 1986, Julian date 301, ten-vane pumps for all 1987 THM 700-R4 production and service replacement transmission assembly (SRTA) models.
SERVICE ACTION
When using the ten-vane pump body assembly to service a THM 700-R4 transmission, mate the new pump body to the pump cover taken from the transmission's existing oil pump.
Figure No. 2 -Ten-Vane Pump Body Assembly:
SERVICE PARTS INFORMATION
8649964 - ten-vane pump body assembly (Figure No. 2) 1985-1987 models.
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.
SERVICE MANUAL REFERENCE
Refer to the oil pump assembly section of the 1987 THM 700-R4 unit repair service manual.
SERVICE NOTES
Seven-vane pump body assemblies, part number 8649950, should normally 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 1985 through 1986 model exhibiting a whine or moan condition and all 1987 THM 700-R4 transmission models.
Figure No. 2 -Ten-Vane Pump Body Assembly:
Figure No. 2
Ten-Vane Pump Body Assembly
002 SEAL ASSEMBLY, OIL NO. 003 BUSHING, PUMP BODY DESCRIPTION 094 RETAINER, FRONT HELIX SEAL 203 BODY, PUMP 204 RING, OIL SEAL (Slide to wear plate) 205 SEAL, "O" RING (Slide seal back-up) 206 SLIDE, PUMP 207 SPRING, PIVOT PIN 208 PIN, PIVOT SLIDE 209 SPRING, PUMP SLIDE (OUTER) 210 SUPPORT, PUMP SLIDE SEAL 211 SEAL, PUMP SLIDE 212 RING, PUMP VANE 213 GUIDE, ROTOR 214 ROTOR, OIL PUMP 215 VANE, PUMP