HARSH SHIFT CONDITIONS AND ON CAR SERVICE INFORMATION

Subject: HARSH SHIFT CONDITIONS AND ON-CAR SERVICE INFORMATION FOR HARSH 3-2 DOWNSHIFTS

Model and Year: 1985-90 CELEBRITY WITH 4T60 AUTOMATIC TRANSMISSION 1990-92 LUMINA WITH 4T60 AUTOMATIC TRANSMISSION

THIS BULLETIN CANCELS AND SUPERSEDES DEALER SERVICE BULLETIN NO. 90-140-7A, DATED JANUARY 1990. THE 3-2 CONTROL VALVE SPRING LISTING HAS BEEN UPDATED AND THE 1991-92 MODEL YEARS HAVE BEEN ADDED. ALL COPIES OF 90-140-7A SHOULD BE DISCARDED.

IMPORTANT: Before performing any service, verify the customer's concern is a 3-2 downshift and not a 2-1 downshift concern. A TECH 1 or other scan tool can be used as an aid to make this determination. Also, it would be an aid for diagnosis to put the transaxle in manual 3rd, or 2nd before and after the concern to determine actual gears of the shift complaint.

NOTICE: DO NOT USE General Motors limited slip differential lubricant additive or equivalent to eliminate undesirable "shift-feel:' reduce harsh shifting, or to minimize torque converter apply/release "shudder' " This will prematurely distress the clutches and bands in the transaxle/transmission by elongating shift-engagement times and increasing slippage between surfaces, even though it might provide better shift-feel for the customer at first. Also, the static capacity (a measure of load-holding capacity) will be reduced by at least 50 percent (i.e., the transaxle/transmission will only handle one half the Combined Gross Vehicle Weight as it did before without slipping).

THE BOTTOM LINE: The customer will be pleased at first, but will be back to the dealership with a distressed transaxle/transmission.

BULLETIN COVERS:

Harsh 3-2 shift conditions and specific service information which applies to the correction of these conditions. Before resorting to the 3-2 Service Packages available, verify that the harsh condition is not caused by the following:

- Vacuum Leaks (low vacuum supply to the vacuum modulator) Remember, the available vacuum will be less at higher altitudes. Also, a restricted exhaust (plugged catalytic converter) can cause a low vacuum. Measure exhaust system pressure as outlined in Section 6F of the Service Manual.

- Faulty Vacuum Modulator (19) Check for proper modulator function as outlined in Section 7 (Transaxle Unit Repair) of your Service Manual. Also verify the modulator valve (1 7) moves freely in its bore and is free of nicks or burrs.

- Sticking 1-2 Servo Control Valve (373) in Control Valve Assembly (35)

- Sticking 3-2 Control Valve (340) in Control Valve Assembly (35)

- Missing or Mislocated Checkballs (2, 4, 12) (refer to Figure 2)

- Sticking 3-2 Coastdown Valve (218) in Oil Pump Assembly (44)

- Improper TN Cable Adjustment (refer to Section 7A of your Service Manual for the proper TN cable adjustment procedure)

IA. VERY HARSH PART THROTTLE 3-2 SHIFT AT 20-40 MPH ---------------------------------------------------- 1985 - 1990 A Cars 1990 W CARS

Service Procedure:

A part throttle downshift is a quick apply of the accelerator pedal beyond a medium throttle position (approximately 1/2 of accelerator pedal travel), forcing a downshift.

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 ensure it is seating properly.

IB. HARSH 3-2 AND/OR 4-2 SHIFTS - 1985-90 A Cars AND 1990 W CARS -----------------------------------------------------------------

Service Procedure:

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 .46 mm (.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 engines 1986 - All models EXCEPT 2.8L engines with transaxles built prior to July 21, 1986 (Julian Date 202)

Service Procedure:

An intermittent harsh 3-2 shift may be caused by a broken 3-2 line control retainer (435) (refer to 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 the 3-2 line control valve moves freely in its bore.

Service Parts Information:

Part Number Description ----------- ------------ 8658678 Retainer, 3-2 Line Control

Parts are currently available from GMSPO.

II. HARSH 3-2 SHIFT "High Altitude Only" 1985-1990 A Car 1990-92 W-Car ----------------------------------------------------------

Service Procedures:

A harsh 3-2 shift condition at high altitude may be corrected by installing the appropriate Service Package containing:

(1) 3-2 Control Valve Spring (341) (refer to Figure 5) (2) Spacer Plate Gaskets (3) Instruction Sheets

IMPORTANT: Service replacement Transaxle Assemblies (SRTA) are built with original calibrations and may need to be updated with a service 3-2 control valve spring per customer requirements.

Service Parts Information:

3-2 Control Valve Spring Transaxle Model Identification Package Number (refer to Figure 1) --------------------------------------------------------------- 8646979 2WWH 8646980 2YBH, 2YCH, 2YKH 8646982 2WFH

8646979 1WWH, 1WSH, 1WXH, 1PAH 8646980 1YDH, 1CHH, 1YHH, 1CJH, 1YSH, 1CAH, 1YTH,1CBH 8646981 1WMH, 1BHH 8646982 1WJH, 1BJH, 1WPH, 1BWH, 1WFH, 1BDH, 1WDH, 1BAH

8646979 OPAH, OWXH 8646980 OAAH, OABH, OAFH, OANH, OATH, OBFH, OKCH, OKDH, OKPH, OKRH, OKLH, OWHH 8646981 OBHH, OWMH 8646982 OBAH, OBDH, OBWH, OBJH, OCJH, OCHH, OWDH, OWFH, OWPH, OWJH 8646993 OLMH, OLNH, OYKH, OYLH, OYSH, OYTH, OYDH, OYHH 8662932 OAJH, OBPH, OKHH, OWNH

8646953 9AAH, 9ABH, 9AFH, 9ANH, 9ATH, 9AJH 8646980 9BPH, 9WRH 8646981 9BHH, 9PAH, 9WBH, 9WCH 8646982 9BAH, 9BDH, 9BJH, 9BWH, 9YCH, 9YAH, 9YBH, 9YJH, 9YFH 8646993 9BFH, 9BMH, 9WUH, 9WZH, 9VYH 8646994 9CDH, 9CLH, 9CPH, 9CYH, 9CZH 8662932 9PBH, 9WLH, 9WKH 8675936 9ACH, 9ADH, 9AHH (Use ALL components in package EXCEPT labels) 8646979 8FCH 8646982 8BKH, 8FBH 8646993 8BJH, 8BRH, 8BTH, 8BYH, 8FJH

8646979 7FCH, 7FZH 8646982 7FBH, 7FKH 8646993 7FJH, 7FNH, 7FRH, 7FTH

8646979 6BCH, 6BDH, 6BMH, 6BZH, 6FCH, 6FZH 8646980 6BAH 8646981 6ACH, 6AWH 8646982 6AAH, 6AMH, 6AFH, 6APH, 6ASH, 6AYH, 6BBH, 6BHH, 6FBH 8646983 6CMH, 6CNH, 6CFH 8646992 6BLH, 6BTH, 6BYH 8646993 6FTH, 6FYH

8646979 5BXH 8646981 5ACH, 5AYH, 5BWH 8646982 5AMH 8646983 5CMH, 5CNH 8646993 5BRH, 5CPH, 5CWH 8646994 5BVH

Parts are currently available from GMSPO.

Service Manual Reference:

Refer to the HYDRA-MATIC 4T60 (ME9) Automatic Transaxle Unit Repair Table of Contents for Control Valve Assembly Service Information.

Service Notes:

Before installing 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.

111. HARSH 3-2 SHIFT **Low Altitude* Only** 1985-1990 A Car 1990-92 W Car

*Areas other than the Designated High Altitude Counties listed in Figure 4. ----------------------------------------------------------------------------

Service Procedure:

A harsh 3-2 shift at low altitude in a 1991 or 1992 model may be corrected by installing the appropriate service package which contains:

(1) 3-2 Control Valve Spring (341) (refer to Figure 5) (2) Spacer Plate Gaskets (3) Instruction Sheet

IMPORTANT: Service Replacement Transaxle Assemblies (SRTA) are built with original calibrations and may need to be updated with a service 3-2 control valve spring per customer requirements.

Service Parts Information:

3-2 Control Valve Spring Transaxle Model Identification Package Number (refer to Figure 1) --------------- ------------------------------ 8646979 2YBH, 2YCH, 2YKH 8646993 2WFH 8662907 2WWH 8646979 1YDH, 1CHH, 1YHH, 1CJH, 1YSH, 1CAH, 1YTH, 1CBH 8646980 1WMH, 1BHH 8646993 1WFH, 1BDH, 1WDH, 1BAH, 1WJH, 1BJH, 1WPH, 1BWH 8662907 1PAH 8646979 OYKH, OYLH, OBFH, OYDH, OYHH, OWHH 8646980 OAAH, OABH, OAFH, OANH, OATH, OBHH, OKCH, OKDH, OKPH, OKRH, OKLH, OWMH 8646981 OCHH, OCJH 8646993 OBAH, OBDH, OBWH, OBJH, OWDH, OWFH, OWPH, OWJH 8662907 OPAH, OWXH 8662932 OAJH, OKHH 8675962 OBPH, OWNH 8675963 OLMH, OLNH, OYSH, OYTH 8646953 9AAH, 9ABH, 9AFH, 9AJH, 9ANH, 9ATH, 9WTH 8646980 9BFH, 9BMH, 9WUH, 9WZH, 9VYH 8646981 9BAH, 9BDH, 9BJH, 9BWH, 9YAH, 9YBH, 9YJH, 9YFH, 9YCH 8646993 9BHH, 9PAH, 9WBH, 9BCH 8662932 9BPH, 9WRH 8675936 9ACH, 9ADH, 9AHH, (Use ALL components in package EXCEPT labels)

8646979 8FJH, 8BJH, 8BTH, 8BYH 8646980 8BRH 8646993 8FBH, 8BKH 8662932 8FCH

8646979 7FJH, 7FNH, 7FRH, 7FTH 8646993 7FBH, 7FKH 8662932 7FCH, 7FZH

8646979 6BAH, 6BLH, 6BTH, 6BYH, 6FTH, 6FYH 8646981 6BBH 8646982 6BHH 8646993 6FBH 8646994 6CNH, 6CMH, 6CFH 8662907 6BCH, 6BDH, 6BMH, 6BZH 8662932 6FCH, 6FZH

Parts are currently available from GMSPO.

Service Manual Reference:

Refer to the HYDRA-MATIC 4T60 (ME9) Automatic Transaxle Unit Repair Table of Contents for Control Valve Assembly Informafion.

IV. HARSH 3-2 SHIFT MANEUVER AT 17-20 MPH - 1985-1/2 - 1986 A Cars ------------------------------------------------------------------- A 3-2 shift maneuver is obtained by allowing the vehicle to coastdown to 17-20 mph (with closed or zero throttle) and then stepping into the throttle to obtain a 3-2 shift.

Service Procedure:

At tart 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 Package Idenfification Number Package Contents (Refer to Fig. 1) ------- ---------------- ----------------- 8646995 (1) Oil Pump Body Assembly Complete 6AAH, 6ACH, 6ADH, (1) Release Cover Gasket 6AFH, 6AMH, 6ANH, (1) Plug & Release Cover Pipe Asm. 6APH, 6ARH, 6ASH, (1) Conduit Clip 6ATH, 6AWH, 6AYH, 5AM, 5AF

8646996 (1) Oil Pump Body Assembly Complete 6BAH, 6BBH, 6BCH, (1) Release Cover Gasket 6BDH, 6BHH, 6BLH, (1) Plug & Release Cover Pipe Asm. 6BMH, 6BSH, 6BTH, (1) Conduit Clip 6BYH, 6BZH, 6CFH, 6CMH, 6CNH, 6HBH, 6HJH 5BR, 5BV, 5BW, 5CM 5CN, 5HJ, 5HA

Parts are currently available from GMSPO.

Service Manual Reference:

Refer to the 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 11 of this bulletin.

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

V. HARSH UPSHIFTS - HIGH ALTITUDE ONLY - 1985-86 A Cars with 2.8L engines ---------------------------------------

Service Procedure:

Harsh upshifts for ALL GEARS 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:

A Cars with 2.81 Engines Only (1) Vacuum Modulator Assembly (1) Modulator Valve (1) O-Ring Seal (1) Instruction Sheet

Service Parts Information:

Service Package Transaxle Model Identification Number (Refer to Figure 1) -------------- ------------------------------ 8646956 6CFH, 6CMH, 6HBH, 6HJH 5CM, 5CN, 5CP, 5CW, 5HA, 5HJ, 5HT

8646966 6AAH, 6ACH, 6AFH, 6AMH 5AF, 5AM

8646967 6ADH,6ARH

Parts are currently available from GMSPO.

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 Number Vehicle Application ----------- ------------------ 14062624 A Car

Parts are currently available from GMSPO.

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.