HARSH SHIFT CONDITIONS AND ON CAR SERVICE INFORMATION
MODELS AFFECTED: 1985-1990 THM4T60 (HYDRA-MATIC 440T4) TRANSAXLES
THIS BULLETIN IS BEING REVISED TO CORRECT THE PART NUMBER LISTINGS. SOME PARTS ARE LISTED IN WRONG AREAS. PLEASE DISCARD BULLETIN 90-7440-7.
IMPORTANT: Before performing any service, make sure to diagnose the specific shift conditions and altitude that affects vehicle performance. DO NOT assume that every condition listed applies to the vehicle.
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 transaxles/transmissions 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%, i.e. The transaxle/transmission will only be able to handle 1/2 the combined gross vehicle weight as it did before without slipping.
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). 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.
- 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)
- Improper TV cable set (3-2 downshifts only)
Before performing any service on the transaxle, verify that the customer concern is a 3-2 downshift or 4-2 and not a 2-1 downshift or harsh TCC/VCC apply/release. A TECH 1 or other scan tools can be used as an aid to make this determination. The TECH 1 or other scan tools will not service all model years; instead use GM Dealer Equipment TCC tester model GM-1 or GM Dealer Equipment Torque Convertor Clutch Tester part number 091-00001 to determine if the shift concern is TCC/VCC related. Also, it would be an aid for diagnosis to put the transaxle in Manual 4th, 3rd or 2nd before and after concern to determine actual gears of the shift complaint. This will help ensure that the customer concern will be addressed.
VERY HARSH PART THROTTLE 3-2 SHIFT AT 20-40 MPH
1985-90 440T4
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 insure it is seating properly.
HARSH 3-2 AND/OR 4-2 SHIFTS - 1985-90 440T4
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.
INTERMITTENT HARSH PART THROTTLE 3-2 SHIFT
1985-1/2 - All Models Except with 2.8L or 3.0L engines 1986 - All Models Except 2.8L or 3.0L engines with transaxles built prior to 7-21-86 (Julian Date 202)
SERVICE PROCEDURE
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
Parts are currently available from GMSPO.
HARSH 3-2 SHIFT - HIGH ALTITUDE ONLY
1985-90 440T4
SERVICE PROCEDURE
A harsh 3-2 shift condition at high altitude may be corrected by installing the appropriate Service Package (package 8675936 contains more components) that contains:
(1) 3-2 Control Valve Spring (Item #341, Figure 5) (2) Spacer Plate Gaskets (1) Instruction Sheet
IMPORTANT: Service Replacement Transaxle Assemblies (S.R.T.A.) are built with original calibrations and may need to be updated with service 3-2 control valve springs per customer requirements.
SERVICE PARTS INFORMATION
3-2 Control Valve Spring Transaxle Model Identification Pkg. Number (Refer to Figure 1) ----------- -------------------- 8646980 OAAH, OABH, OAFH, OANH, OATH 8662932 OAJH 8646993 OLMH, OLNM 8646982 OBAH, OBDH, OBWH, OBJH 8646981 OBHH 8646980 OBFH 8662932 OBPH 8646979 OPAH 8646993 OYKH, OYLH 8646982 OCJH, OCHH
8646953 9AAH, 9ABH, 9AFH, 9ANH, 9ATH, 9AJH 8675936 9ACH, 9ADH, 9AHH (use all components in package except labels) 8646982 9BAH, 9BDH, 9BJH, 9BWH 8646993 9BFH, 9BMH 8646981 9BHH, 9PAH, 9WBH, 9WCH 8646980 9BPH, 9WRH 8646994 9CDH, 9CLH, 9CPH, 9CYH, 9CZH 8662932 9PBH, 9WLH, 9WKH 8646993 9WUH, 9WZH, 9VYH 8646982 9YAH, 9YBH, 9YJH, 9YFH, 9YCH
8646993 8BJH, 8BRH, 8BTH, 8BYH, 8FJH 8646982 8BKH, 8FBH 8646979 8FCH
8646982 7FBH, 7FKH 8646979 7FCH, 7FZH 8646993 7FJH, 7FNH, 7FRH, 7FTH
8646982 6AAH, 6AMH, 6AFH, 6APH, 6ASH, 6AYH, 6BBH, 6BHH, 6FBH 8646981 6ACH, 6AWH 8646980 6BAH 8646979 6BCH, 6BDH, 6BMH, 6BZH, 6FCH, 6FZH 8646992 6BLH, 6BTH, 6BYH 8646983 6CMH, 6CNH, 6CFH 8646993 6FTH, 6FYH
8646981 5AC, 5AY, 5BW 8646993 5BR, 5CP, 5CW 8646979 5BX 8646982 5AM 8646994 5BV 8646983 5CM, 5CN
Parts are currently available from GMSPO.
SERVICE MANUAL REFERENCE
Refer to the THM 440T4/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.
HARSH 3-2 SHIFT - *AT LOW ALTITUDE
- 1986 Vehicles with 2.8L, 3.0L and 3.8L Engines - 1987 Vehicles with 3.8L Engines - 1988 Vehicles with 3.8L Engines - 1989-90 All with 440T4
*Areas other than the Designated High Altitude Counties listed in Figure 8
SERVICE PROCEDURE
A harsh 3-2 shift at low altitude in a 1986 through 1990 model may be corrected by installing appropriate service package (package 8675936 contains more components) that contains:
(1) 3-2 Control Valve Spring (Item #341, Figure 5) (2) Spacer Plate Gaskets (1) Instruction Sheet
IMPORTANT: Service Replacement Transaxle Assemblies (S.R.T.A.)are built with original calibrations and may need to be updated with service 3-2 control valve springs per customer requirements.
SERVICE PARTS INFORMATION
3-2 Control Valve Spring Transaxle Model Identification Pkg. Number (Refer to Figure 1) ----------- ------------------- 8646980 OAAH, OABH, OAFH, OANH, OATH 8662932 OAJH 8675963 OLMH, OLNM 8646979 OBFH 8646993 OBAH, OBDH, OBWH, OBJH 8646980 OBHH 8675962 OBPH
8662907 OPAH 8646979 OYKH, OYLH 8646981 OCHH, OCJH
8646953 9AAH, 9ABH, 9AFH, 9AJH, 9ANH, 9ATH 8675936 9ACH, 9ADH, 9AHH (use all components in package except labels) 8646981 9BAH, 9BDH, 9BJH, 9BWH, 9YAH, 9YBH, 9YJH, 9YFH, 9YCH 8646993 9BHH, 9PAH, 9WBH, 9WCH 8646980 9BFH, 9BMH, 9WUH, 9WZH, 9VYH 8662932 9BPH, 9WRH 8646953 9WTH
8662932 8FCH 8646980 8BRH 8646993 8FBH, 8BKH 8646979 8FJH, 8BJH, 8BTH, 8BYH
8662932 7FCH, 7FZH 8646993 7FBH, 7FKH 8646979 7FJH, 7FNH, 7FRH, 7FTH
8646979 6BAH, 6BLH, 6BTH, 6BYH, 6FTH, 6FYH 8662907 6BCH, 6BDH, 6BMH, 6BZH 8646981 6BBH 8646982 6BHH 8646994 6CNH, 6CMH, 6CFH 8646993 6FBH 8662932 6FCH, 6FZH
Parts are currently available from GMSPO.
SERVICE MANUAL REFERENCE
Refer to the THM 440T4/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.
HARSH 3-2 SHIFT MANEUVER AT 17-20 MPH
1985-1/2 - 1986 440T4
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 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 Package Identification Number Package Contents (Refer to Fig. 1) ------ ---------------- ----------------- 8646995 (1) Oil Pump Body Asm. 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 Asm. 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 THM 440T4/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 indesignated high altitude areas (Figure 8), 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 1-2 servo control valve move freely in their bores.
HARSH 3-2 COASTDOWN BUMP 3.8L AT 15-22 MPH
1985-87 440T4 transaxles built prior to 12-18-86 (Julian Date 352) and 3.8L engines
SERVICE PROCEDURE
A coastdown bump is obtained by allowing the vehicle to coastdown to 15-22 mph (with closed or zero throttle) and a sudden and forceful apply of the 1-2 band is felt when the transaxle shifts from third to second gear. 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 Number Description ----------- ----------- 8668123 1-2 Servo Cushion Spring (Item #559, Figure 7)
Parts are currently available from GMSPO.
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.
HARSH UPSHIFTS - HIGH ALTITUDE ONLY
1985-86 440T4 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.
SERVICE PARTS INFORMATION
Service Package Number Transaxle Model 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
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
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.
