DELAYED, HARSH ENGAGEMENT SLIP ON ACCELERATION

BULLETIN COVERS:

Service information on the correct location of the forward clutch checkball (#12) and the possible effects of installing the checkball in the wrong location.

NOTICE:

1987 Service Manuals refer to the forward clutch checkball (#55B) in the auxiliary valve body as #5. To avoid confusion with the lo and reverse #5 checkball in a THM 700-R4 transmission produced without an auxiliary valve body (Figure 2, #55B), the forward clutch checkball has been changed to #12 (Figure 3, #55B).

DATE OF PRODUCTION CHANGE:

By October 6, 1986 (Julian Date 279) (Figure 1) all 1987 THM 700-R4 transmissions were produced with an auxiliary valve body (377) for an improved drive engagement shift feel. As part of this change, the 10 and reverse checkball (#5) located in the valve body assembly (Figure 2) was eliminated, and a new forward clutch checkball (#12 Figure 3) was added to the Auxiliary Valve Body. All 1987 Service Replacement Transmission Assembly (SRTA) units have this change.

SERVICE ACTION:

When servicing any 1982 through 19a7 THM 700-R4 transmission without an auxiliary valve body (Figure 3), the lo and reverse checkball (55B, Figure 2) must be located in the control valve body.

When servicing any 1987 THM 700-R4 transmission produced after October 6, 1986 (Julian Date 279) the forward clutch checkball (#12) must be located in the auxiliary valve body ( 5 5B , Figure 3). Do not install a checkball in the control valve body.

NOTICE: If the forward clutch checkball (#12) is installed in either the valve body or over the orificed cup plug (359, Figure 3) in the auxiliary valve body, the following conditions can occur:

- Delayed N-D, P-D or R-D

- Harsh N-D, P-D Shifts

- Slipping on Hard Accelerations

- Forward Clutch Distress

- No Upshift

- 1-2 Tie-Up/Lo-Rev Clutch Distress and 2-4 Band Distress

FIGURE 2 FIGURE 3

Checkball Locations on Checkball Locations on Transmissions without Auxiliary Transmissions with Auxiliary Valve Bodies Valve Bodies,

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.