HARSH SHIFT CONDITIONS AND ON CAR SERVICE INFORMATION

TRANSMISSION APPLICATIONS: SUBJECT: ------------------------- ------- 1985 - 1987 THM 440-T4 HARSH SHIFT CONDITIONS AND ON CAR SERVICE INFORMATION

TRANSMISSION MODELS: VEHICLE APPLICATIONS: ------------------- -------------------- A, C, H, E, K CARS

SUBJECT: -------- Harsh Shift Conditions And On Car Service Information For:

I. Harsh Part Throttle 3-2 Shift Conditions:

A. Very Harsh Part Throttle 3-2 Shift At 32-64 KM/HR (20-40 MPH) B. Harsh 3-2 And/Or 4-2 Shifts C. Intermittent Harsh 3-2 Shifts

II. Harsh 3-2 Shift - High Altitude Only

III. Harsh 3-2 Shift - Low Altitude Only

IV. Harsh 3-2 Shift Maneuver At 27-32 KM/HR (17-20 MPH)

V. Harsh 3-2 Coastdown Bump At 32-64 KM/HR (20-40 MPH) With 3.8L Engine

VI. Harsh Upshifts - High Altitude Only

VEHICLE APPLICATIONS:

A, C, H, E, K Cars

NOTE: This bulletin supersedes Bulletin 86-7440-110, which may now be discarded.

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.

BULLETIN COVERS:

Harsh shift conditions and the specific service information that applies to each of these conditions. However, 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 - 44-61 kPa or 13-18 In Hg required.

- paint in the modulator tube 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).

IA. VERY HARSH PART THROTTLE 3-2 SHIFT AT 32-64 KM/HR (20-40 MPH) - 1985- 1987 A, C, H, E, K Cars

Service Action:

A very harsh part throttle 3-2 shift at 32-64 km/hr (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.

IB. HARSH 3-2 AND/OR 4-2 SHIFTS - 1985-1987 A. C, H, E, K 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.

IC. INTERMITTENT HARSH PART THROTTLE 3-2 SHIFT - 1985 1/2 - All Models except with 2.8L or 3.0L engines; 1986 - All Models except with 2.8L or 3.0L engines and transaxles built prior to 7/2/86 (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 Number Description ----------- ----------- 8658678 Retainer, 3-2 Line Control

II. HARSH 3-2 SHIFT - HIGH ALTITUDE ONLY -1985-1987 A, C, H, E, K* 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 Spring Transaxle Model Package Number Identification (refer to Figure 1) -------------- ---------------------------------- 8646979 7FCH, 7FZH " 6BCH, 6BDH, 6BMH, 6BZH " 5BX

8646980 6BAH " 8646981 6ACH, 6AWH " 5AC, 5AY, 5BW

8646982 7FBH, 7FKH " 6AAH, 6AMH, 6AFH, 6APH, 6ASH, 6AYH, 6BBH, 6BHH " 5AM

8646983 6CMH, 6CNH, 6CFH " 5CM, 5CN

8646992 6BLH, 6BTH, 6BYH

8646993 7FJH, 7FNH, 7FRH, 7FTH " 5BR, 5CP, 5CW

8646994 5BV

Service Manual Reference:

Refer to the THM 440-T4 (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 7 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.

III. HARSH 3-2 SHIFT - *At Low Altitude - 1986 A, C, H, E Cars with 2.8L, 3.0L and 3.8L engines; 1987 A, C, H, E Cars with 3.8L engines. (*Areas other than the Designated High Altitude Counties listed in Figure 7.)

Service Action:

A harsh 3-2 shift at low altitude in a 1986 A, C, H, E, K 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 Spring Transaxle Model Package Number Identification (refer to Figure 1) -------------- --------------- 8646979 7FJH, 7FNH, 7FRH, 7FTH " 6BAH, 6BLH, 6BTH, 6BYH

8646981 6BBH

8646982 6BHH

8646993 7FBH, 7FKH

8646994 6CNH, 6CMH, 6CFH

8662907 6BCH, 6BDH, 6BMH, 6BZH

8662932 7FCH, 7FZH

Service Manual Reference:

Refer to the THM 440-T4 (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 the 1-2 servo control valve move freely in their bores.

IV. HARSH 3-2 SHIFT MANEUVER AT 27-32 KM/HR (17-20 MPH) - 1985-1986 A, C, H, E, K* Cars (*1986 Only)

A 3-2 shift maneuver is obtained by allowing the vehicle to coastdown to 27- 32 km/hr (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. 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:

Package Transaxle Model I.D. Number Package Contents (Refer to Figure 1) ----------------------- ---------------------- 8646995 (1) Oil Pump Body Asm. Complete 6AAH, 6ACH, 6ADH, 6AFH, (1) Release Cover Gasket 6AMH, 6ANH, 6APH, 6ARH, (1) Plug and Release Cover Pipe Asm. 6ASH, 6ATH, 6AWH, 6AYH (1) Conduit Clip 5AM, 5AF

8646996 (1) Oil Pump Body Asm. Complete 6BAH, 6BBH, 6BCH, 6BDH, (1) Release Cover Gasket 6BHH, 6BLH, 6BMH, 6BSH, ' (1) Plug and Release Cover Pipe Asm. 6BTH, 6BYH, 6BZH,6CFH, (1) Conduit Clip 6CMH, 6CNH, 6HBH, 6HJH 5BR, 5BV, 5BW, 5CM, 5CN, 5HJ, 5HA Service Manual Reference: ------------------------- Refer to the THM 440-T4 (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 7), also install the 3-2 control valve spring package described in Section II of this bulletin.

Also ensure that the 3-2 control valve and the 1-2 servo control valve move freely in their bores.

V. HARSH 3-2 COASTDOWN BUMP 3.8L AT 32-64 KM/HR (20-40 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 12-15-860512/349 7FNH 12-11-86/345 7HCH 12-18-86/352 7FRH 12-17-87/351

Service Parts Information:

Part Number Description ----------- ----------- 8646457 1-2 Servo Cushion Spring (Item #559, Figure 6)

Service Notes:

If the above condition persists make sure the 3-2 coastdown valve (located in the oil pump body) i,s not stuck and moves freely in its bore.

VI. HARSH UPSHIFTS - HIGH ALTITUDE ONLY - 1985-1986 Buick, Chevrolet, Oldsmobile, Pontiac A Cars with 20512.8L 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:

Buick, Chevrolet, Oldsmobile, Cadillac C, E, K Cars Pontiac A Cars With 2.8L Engines With 4.1L 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 Package Number Identification (Refer to Figure 1) -------------- ---------------------------------- 8646956 6CFH, 6CMH, 6CNH, 6HBH, 6HJH " 5CM, 5CN, 5CP, 5CW, 5HA, 5HJ, 5HT

8646966 6AAH, 6ACH, 6AFH, 6AMH, " 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 package listed above.

Part Number Vehicle Application ----------- ------------------- 14062624 A Car 1637147 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 or other foreign material.

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.