A/T - Harsh Park/Neutral to Reverse Engagement
88chevy24GMC NUMBER: 88-T-116
GROUP: 7A - Automatic Transmission
DATE: May, 1988
CORPORATE
NUMBER: 877125
SUBJECT: HARSH PARK/NEUTRAL TO REVERSE ENGAGEMENT SHIFT FEEL
MODELS: 1987-1988 C,K,R,V AND G MODELS EQUIPPED WITH THM 400 AUTOMATIC TRANSMISSION AND HAVE A GVWR OF 10,000 LBS AND UNDER
TRANSMISSION MODELS:
FDA, FFA, FMA, FTA, FWA, FZA, LKA, LMA, LTA, LUA, LWA, LZA, FJA, FNA, FPA, FUA, FYA, LBA, LDA, LHA, LJA, FCA, LFA, LRA, LSA
BULLETIN COVERS
Service and parts information concerning harsh park or neutral to reverse engagement shift feel on vehicles with a Gross Vehicle Weight Rating (GVWR) of 10,000 lbs. and under. Included are: control valve assembly, valve body gaskets, valve body spacer plate, case assembly with an additional check ball and orificed cup plug.
NOTICE
The new case assembly, control valve assembly, gaskets, and check ball will be included on all THM 400/475 models. However, only the vehicles that have GVWR of 10,000 lbs. and under will have the new garage shift spacer plate and orifice cup plug. The vehicles with GVWR over 10,000 lbs. have increased clutch capacity requirements which may result in burned clutches if this garage package is installed.
IT IS NOT RECOMMENDED THAT VEHICLES WITH GVWR OVER 10,000 LBS. BE UPDATED WITH THIS PACKAGE.
FIGURE 1 - THM 400 TRANSMISSION IDENTIFICATION INFORMATION:
DATE OF CHANGE (Figure No. 1)
Beginning November 23, 1987 (Julian Date 327) all THM 400 transmissions with a GVWR of 10,000 lbs. and under were built with a new reverse engagement package.
FIGURE 2 - CASE - VALVE BODY PASSAGES:
FIGURE 3 - PLATE - VALVE BODY SPACER (NON-GARAGE):
FIGURE 4 - PLATE - VALVE BODY SPACER (GARAGE SHIFT):
FIGURE 5 - VALVE BODY OIL PASSAGES:
FIGURE 6 - GASKET - SPACER PLATE TO CASE:
FIGURE 7 - GASKET - SPACER PLATE TO VALVE BODY:
SERVICE ACTION
To service a 1987-1988 THM 400 transmission built prior to November 23,1987 (Julian Date 327) it is necessary to replace the case assembly, spacer plate, and valve body gaskets listed under "Service Parts Information". Refer to Figures 2 through 7.
NOTICE
When installing the park/neutral to reverse engagement shift feel package on a past model transmission built prior to November 23, 1987 (Julian Date 327) the original control valve assembly can be used.
SERVICE PARTS INFORMATION
Model Applications
Part No. Part Description (1987 and 1988 only)
8629970 Package-Case Assembly FDA, FMA, FTA, FZA, LMA,
Case Assembly-Complete LTA, LUA, LZA, FJA, FPA,
Ball FUA, FYA, LBA, LHA, LJA
Plug-Orifice Cup .096" (copper)
8629971 Package-Case Assembly LDA, LFA, LKA, LRA, LSA,
Case Assembly-Complete LWA, FFA, FNA, FWA, FCA
Ball Plug-Orifice Cup .096" (copper) Plug-Orifice Cup .089" (blue/USE ON 4.3L ENGINES ONLY)
8670447 Gasket-Value Body/Spacer Plate ALL MODELS
8670458 Gasket-Case/Spacer ALL MODELS
* Plate-Valve Body Spacer
* Refer to the Service Parts List for correct usage on spacer plates.
SERVICE MANUAL REFERENCE
Please make note of these changes which are not in your 1988 Service Manual. Refer to the THM 400/475 unit repair service manual for proper case, control valve assembly, spacer plate, and gasket replacement procedures. For repairs performed under warranty use:
Labor Op: K7800
Labor Time: 5.2 hrs - C
6.2 hrs. - K Add .2 hr. w/Skid Plate
5.1 hrs. - G 5.0 hrs. - R
6.4 hrs. - V Add .3 hr. w/Skid Plate