A/T - 700 R4 Pump Whine or Moan
Number: 87-66Section: 7A
Date: FEB., 1987
Subject: PUMP WHINE OR MOAN THM 700-R4
Model and Year: 1985-87 PASSENGER CARS AND TRUCKS WITH THM 700-R4 TRANSMISSIONS
FIGURE 1 - THM 700 - R4 - TRANSMISSION I.D. NAMEPLATE:
TO: ALL CHEVROLET DEALERS
A whine or moan on a 1985 through 1987 THM 700-R4 transmission may be caused by line pressure instability in a seven-vane 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.
FIGURE 2 - TEN VANE PUMP BODY ASSEMBLY:
When using the ten-vane pump body assembly to service a THM 700-R4 transmission 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 1985 through 1986 model exhibiting a whine or moan condition and all 1987 THM 700-R4 transmission models.