HARSH SHIFT CONDITIONS AND CAR SERVICE INFORMATION
TRANSMISSION APPLICATIONS: SUBJECT: 1985-89 THM 440_T4/HYDRA- HARSH SHIFT CONDITIONS MATIC 4T-60 (ME9)
TRANSMISSION MODELS: VEHICLE APPLICATIONS: REFER TO EACH CONDITION FOR A, C, E, H, K, W AND Z CARS MODEL USAGE
Bulletin Covers:
Harsh Shift Conditions and On Car Service Information for:
1. Harsh Part Throttle 3-2 Shift Conditions:
A. Harsh Part Throttle 3-2 Shift at 20-40 mph.
B. Harsh 3-2 and/or 4-2 Shifts.
C. Intermittent Harsh 3-2 Shift
2. Harsh 3-2 Shift - High Altitude Only.
3. Harsh 3-2 Shift - Low Altitude Only.
4. Harsh 3-2 Shift Maneuver at 17-20 mph.
5. Harsh 3-2 Coastdown Bump at 15-20 mph With 3.8L Engine.
6. Harsh Upshifts - High Altitude Only.
IMPORTANT: Before performing any service action, make sure to diagnose the specific shift condition and altitude that affects vehicle performance. Do not assume that every condition listed applies to the vehicle. Refer to Figure 1.
Some other items that affect transaxle operation which may also contribute to these harsh shift conditions are:
-Vacuum leaks (low vacuum supply to the vacuum modulator). Required vacuum is 44-61 KPa (13-18 in. Hg.).
-Paint in the modulator tube and/or carbon at the throttle body fitting (vacuum signal should respond quickly to throttle movement) restricting vacuum to the modulator causing a delayed response to throttle movement.
- Sticking modulator valve.
- Sticking 1-2 servo valve.
- Missing checkballs (#2, #4 or #12).
- Misadjusted TV cable (3-2 downshifts only).
NOTE: - A high altitude area is one where the altitude is 1200 meters (4000 ft.) or higher.
1A. - Very Harsh Part Throttle 3-2 Shift at 20-40 mph - 1985-1989 A, C, H, E, K, W Cars
Service Action:
A harsh part throttle 3-2 shift at 20-40 mph may be caused by a missing or mislocated #2 3-2 control checkball (Figure 2) . Remove the valve body to inspect for proper checkball location or damage to the spacer plate. A mislocated checkball may have bent the spacer plate. Also inspect the #12 1-2 servo feed checkball to insure it is seating properly.
1B. - Harsh 3-2 And/Or 4-2 Shifts - 1985-1989 A, C, H, E, K, W Cars
Service Action:
Harsh 3-2 and 4-2 shifts at any altitude may be caused by a missing or partial hole in the spacer plate. Remove the valve body and inspect the spacer plate for a missing or partial governor passage hole (#25) as shown in Figure 3. A partial hole can be drilled out using a #77 drill bit to meet the hole size requirement of .46mm (.018"). If the hole is missing, use the spacer plate gasket and control valve body as a guide to locate and drill the hole, or replace the spacer plate.
1C. - Intermittent Harsh Part Throttle 3-2 Shift - 1985-1/2 - All models except with 2.8L or 3.OL engines. 1986 - All models except with 2.8L or 3.OL engines and trans- axles built prior to 7/21/86 (Julian Date 202)
Service Action:
An intermittent harsh 3-2 shift may be caused by a broken 3-2 line control retainer (Item #435, Figure 4). Remove the transaxle side cover to access the 3-2 line control valve and if necessary replace a broken retainer with the part listed below. Also ensure that the 3-2 line control valve moves freely in its bore.
Service Parts Information:
Part No. Description ------- ----------- 8658678 Retainer, 3-2 Line Control
2. - Harsh 3-2 Shift - High Altitude Only - 1985 - 1988 A, C, H, E, K*, W Cars (*1986 Only)
Service Action:
A harsh 3-2 shift condition at high altitude may be corrected by installing the appropriate Service Package that contains the following items:
(1) 3-2 Control Valve Spring (Item #341, Figure 5)
(2) Spacer Plate Gaskets
(1) Instruction Sheet
Service Parts Information:
3-2 Control Valve Transaxle Model Spring Package No. Identification (refer to Figure 1)
8646979 8FCH 8646979 7FCH, 7FZH 8646979 6BCH, 6BDH, 6BMH, 6BZH, 6FCH, 6FZH 8646979 5BX
8646980 6BAH
8646981 6ACH, 6AWH 8646981 5AC, 5AY, 5BW
8646982 8BKH, 8FBH 8646982 7FBH, 7FKH 8646982 6AAH, 6AMH, 6AFH, 6APH, 6ASH, 6AYH, 6BBH, 6BHH, 6FBH 8646982 5AM
8646983 6CMH, 6CNH, 6CFH 8646983 5CM, 5CN
8646992 6BLH, 6BTH, 6BYH
8646993 8BJH, 8BRH, 8BTH, 8BYH, 8FJH 8646993 7FJH, 7FNH, 7FRH, 7FTH 8646993 6FTH, 6FYH 8646993 5BR, 5CP, 5CW
8646994 5BV
Service Manual Reference:
Refer to the THM 440-T4/HYDRA-MATIC 4T60 (ME9) Automatic Transaxle Unit Repair Table of Contents for control valve assembly service information.
Service Notes:
Before installing a Service Replacement Transaxle Assembly (SRTA) in areas designated as "high altitude", install the new 3-2 control valve spring. Refer to Figure 8 for a geographical listing of high altitude areas.
Also ensure that the 3-2 control valve and the 1-2 servo control valve move freely in their bores.
3. - Harsh 3-2 Shift - *At Low Altitude - 1986 A, C, H, E Cars with 2.8L, 3.OL and 3.8L engines; 1987 A, C, H, E Cars with 3.8L engines; 1988 A, C, H, E Cars with 3.8L engines
*Areas other than the Designated High Altitude Counties listed in Figure 8.
Service Action:
A harsh 3-2 shift at low altitude in an 1986 through 1988 A, C, H, E Car may be corrected by installing a service package that contains:
(1) 3-2 Control Valve Spring (Item #341, Figure 5).
(2) Spacer Plate Gaskets
(1) Instruction Sheet
Service Parts Information:
3-2 Control Valve Transaxle Model Spring Package No. Identification (refer to Figure 1)
8646979 7FJH, 7FNH, 7FRH, 7FTH 8646979 6BAH, 6BLH, 6BTH, 6BYH, 6FTH, 6FYH 8646981 6BBH 8646982 6BHH 8646993 6FBH 8646993 7FBH, 7FKH 8646994 6CNH, 6CMH, 6CFH 8662907 6BCH, 6BDH, 6BMH, 6BZH 8662932 6FCH, 6FZH 8662932 7FCH, 7FZH 8662932 8FCH 8646979 8FJH, 8BJH, 8BTH, 8BYH 8646993 8FBH, 8BKH 8646980 8BRH
Service Manual Reference:
Refer to the THM 440-T4/HYDRA-MATIC 4T60 (ME9) Automatic Transaxle Unit Repair Table of Contents for Control Valve Assembly Information.
Service Notes:
When servicing a transaxle for this condition, also ensure that the 3-2 control valve and 1-2 servo control valve move freely in their bores.
4. - Harsh 3-2 Shift Maneuver at 17-20 mph - 1985-1/2 - 1986 A, C, H, E, K* Cars (*1986 Only)
A 3-2 shift maneuver is obtained by allowing the vehicle to coastdown to 17-20 mph (with closed throttle) and then stepping into the throttle to obtain a 3-2 shift.
Service Action:
At start of production (SOP) 1987, an orifice pipe was added between the 1-2 servo release cover plate and the 3-2 coastdown valve to allow a smoother second gear apply (Figure 6). The four new parts installed as a set will service certain past model transaxles with a harsh 3-2 shift maneuver condition.
Service Parts Information:
Transaxle Model I.D. Package No. Package Contents (Refer to Figure 1) ----------- ---------------- -------------------- 8646995 (1) Oil Pump Body Asm. Complete 6AAH, 6ACH, 6ADH, 6AFH, 6AMH, 6ANH (1) Release Cover Gasket 6APH, 6ARH, 6ASH, 6ATH, 6AWH, 6AYH (1) Plug and Release Cover Pipe Asm. 5AM, 5AF
8646996 (1) Oil Pump Body Asm. Complete 6BAH, 6BBH, 6BCH, 6BDH, 6BHH, 6BLH (1) Release Cover Gasket 6BMH, 6BSH, 6BTH, 6BYH, 6BZH, 6CFH (1) Plug and Release Cover Pipe Asm. 6CMH, 6CNH, 6HBH, 6HJH (1) Conduit Clip 5BR, 5BV, 5BW, 5CM, 5CN, 5HJ, 5HA
Service Manual Reference:
Refer to the THM 440-T4/HYDRA-MATIC 4T60 (ME9) Automatic Transaxle Unit Repair Table of Contents for appropriate service information.
Service Notes:
If the new pump body assembly has a "one terminal" 3rd clutch switch, remove it and replace with the "two terminal" 3rd clutch switch from the original pump body assembly.
When servicing a transaxle for the above described condition in designated high altitude areas (Figure 8), also install the 3-2 control valve spring package described in Section 2 of this bulletin.
Also ensure that the 3-2 control valve and the 1-2 servo control valve move freely in their bores.
5. - Harsh 3-2 Coastdown Bump 3.8L At 15-20 mph - 1985-1987 A, C, H, E Cars with transaxles built prior to 12/18/86 (Julian Date 352) and 3.8L engines
Service Action:
A harsh 3-2 coastdown bump may be caused by the 1-2 servo cushion spring. This condition may be corrected by replacing the 1-2 servo cushion spring with the part listed below. Refer to the chart below to determine the transaxle model and Julian Date when the new springs were first used in production units.
Transaxle Build Date/ Transaxle Build Date/ Model Julian Date Model Julian Date --------- ----------- --------- ----------- 7FBH 12/11/86-345 7FSH 12/11/86-345 7FCH 12/11/86-345 7FTH 12/11/86-345 7FJH 12/15/86-349 7FZH 12/12/86-346 7FKH 12/11/86-345 7HAH 12/15/86-349 7FNH 12/11/86-345 7HCH 12/18/86-352 7FRH 12/17/86-351
Service Parts Information:
Part No. Description ------- ----------- 8668123 1-2 Servo Cushion Spring (Item #559, Figure 7)
Service Notes:
If the above condition persists make sure the 3-2 coastdown valve (located in the oil pump body) is not stuck and moves freely in its bore.
6. - Harsh Upshifts - High Altitude Only - 1985-1986 Buick, Chevrolet, Oldsmobile, Pontiac Cars with 2.8L Engines and Cadillac C, E, K* Cars (*1986 Only) with 4.1L Engines
Service Action:
Harsh upshifts at high altitudes may be caused by high line pressure due to low engine vacuum. This condition may be corrected on certain transaxle models by installing the appropriate aneroid modulator
Service Package.
Based on vehicle applications, each package contains:
Cadillac C, E, K Cars Buick Chevrolet, Oldsmobile, Pontiac With 4.1L Engines A Cars With 2.8L Engines Only --------------------- ------------------------------------ (1) Vacuum Modulator Asm. (1) Vacuum Modulator Asm. (1) Modulator Valve (1) Modulator Valve (1) O-Ring Seal (1) O-Ring Seal (1) Spacer Plate (1) Instruction Sheet (5) Gaskets (1) Cup Plug (orificed) (2) Instruction Sheets
Service Parts Information:
Service Transaxle Model Identification Package No. (Refer to Figure 1)
8646956 6CFH, 6CMH, 6CNH, 6HBH, 6HJH 8646956 5CM, 5CN, 5CP, 5CW, 5HA, 5HJ, 5HT
8646966 6AAH, 6ACH, 6AFH, 6AMH 8646966 5AF, 5AM
8646967 6ADH, 6ARH
Service Notes:
A new vacuum line from the engine to the vacuum modulator must also be installed when using the service packages listed above.
Part No. Vehicle Application -------- ------------------- 14062624 A Car 1643771 C Car 1641441 E, K Cars
Other items affecting harsh upshift conditions are:
- engine vacuum leaks.
- sticking modulator valve.
- restrictions in the vacuum lines such as paint in the modulator tube and/or carbon at the throttle body fitting.
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.
