New transmission oil pump assemblies with Nodular Iron Vane Rings entered production April 28, 1987 (Julian date 118) on THM 700-R4 transmissions. This change also applies to SRTA.
Beginning June 17, 1987 (Julian date 168) all THM 200-4R began production with the new rings. (Refer Figure 1)
The new design vane rings (item 212, Figures 2 and 3) will reduce the possibility of vane ring distress and can be used on any 1982 through 1987 THM 700-R4 transmission or any 1981 through 1987 THM 200-4R transmission, and it is recommended that the new iron pump vane rings be used when replacement of the vane rings becomes necessary.
THM 700-R4 transmission only:
8657531 Pump Vane Ring (2 required)
THM 200-4R transmission only:
8657692 Pump Vane Ring (2 required)
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.