HARSH SHIFT CONDITIONS AND ON CAR SERVICE INFORMATION

SUBJECT: SERVICE INFORMATION FOR HARSH 3-2 DOWNSHIFTS AND OTHER HARSH SHIFT CONDITIONS

MODELS AFFECTED: 1985 -1990 DE VILLES AND FLEETWOODS 1986-1990 ELDORADOS AND SEVILLES WITH HYDRA-MATIC 4T60 (THM 44O-T4)

This bulletin cancels and replaces Service bulletin T-89-93 which should be discarded.

Some 1985 - 1990 DeVilles and Fleetwoods and 1986 - 1990 Eldorados and Sevilles may experience one or more of the following conditions:

I. Very Harsh Part Throttle 3-2 Shift At 20-40 MPH: 1985-1990 DeVilles and Fleetwoods and 1986-1990 Eldorados and Sevilles.

II. Harsh 3-2 and/or 4-2 Shifts: 1985-1990 DeVilles and Fleetwoods and 1986-1990 Eldorados and Sevilles.

III. Intermittent Harsh Part Throttle 3-2 Shift: 1985-1986 DeVilles and Fleetwoods and 1986 Eldorados and Sevilles.

IV. Harsh 3-2 Shift At High Altitude Only: 1985-1990 DeVilles and Fleetwoods and 1986-1990 Eldorados and Sevilles.

V. Harsh 3-2 Shift At Low Altitude Only: 1985-199O DeVilles and Fleetwoods and l986-1990 Eldorados and Sevilles.

VI. Harsh 3-2 Shift Maneuver At l7-2O MPH: 1985-1986 DeVilles and Fleetwoods and l986 Eldorados and Sevilles.

VII. Harsh 3-2 Coast Down Bump At 15-22 MPH: 1989 DeVilles, Fleetwoods, Eldorados, and Sevilles.

VIII. Harsh Upshifts At High Altitude Only: 1985-1986 DeVilles and Fleetwoods and 1986 Eldorados and Sevilles.

IMPORTANT- Before performing any service, verify the customer's concern is a 3-2 downshift and not a 2-1 downshift concern. ECM status light displays for fourth and third gears (where applicable) in diagnostics can be used as an aid to make this determination. Also, it would be an aid for diagnosis to put the transaxle in manual third or second before and after the concern to determine actual gears of the shift complaint.

This bulletin covers the listed harsh shift conditions and specific service information which apply to the correction of these conditions. Before resorting to the Service Packages available verify that the harsh shift condition is not caused by the following:

0 Incorrect Vacuum Response to the Modulator. Refer to Service bulletin T-87-33A. 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 Information Manual.

0 Faulty Vacuum Modulator (19). Check for proper modular function as outlined in Section 7 (Transaxle Unit Repair) of the appropriate Service Information Manual. Also verify the modulator valve (17) moves freely in its bore and is free of ticks and burrs.

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

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

0 Missing or Mislocated Checkballs (2, 4, 12). (Refer to Figure 2).

- Sticking 3-2 Coast Down Valve (218) in Oil Pump Assembly (44).

- Improper TV Cable Adjustment.

(Refer to Section 7A of the appropriate Service Information Manual for the proper TV cable adjustment procedure.)

IMPORTANT- DO NOT USE General Motors limited slip differential lubricant additive or equivalent to eliminate undesirable "shift-feel" to 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. The customer will be pleased at first but will be back to the dealership with a distressed transaxle/transmission.

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. Refer to 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.

Service Procedure:

Harsh 3-2 and 4-2 shifts at any altitude maybe 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.

Service Procedure:

An intermittent harsh 3-2 shift maybe 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.

P/N Description --- ----------- 8658678 Retainer, 3 - 2 Line Control

Parts are currently available from GMSPO.

* - Refer to Figure 8 for designated high altitude counties.

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.

3 - 2 Control Valve Spring Transaxle Model Identification Package Number Refer to Figure 1 -------------------------- ------------------------------ 8646980 OAAH, OABH, OAFH, OANH, OATH, OBFH, OKCH, OKDH, OKPH, OKRH, OKLH, OWNH 8662932 OAJH, OBPH, OKHH, OWNH

8646953 9AAH, 9ABH, 9AFH, 9ANH, 9ATH, 9AJH 8675936 9ACH, 9ADH, 9AHH (Use all components in package except labels) 8646981 6ACH, 6AWH 8646982 6AAH, 6AMH, 6AFH, 6APH, 6ASH, 6AYH, 6BBH, 6BHH, 6FBH

8646981 5ACH, 5AYH, 5BWH 8646982 5AMH

Parts are currently available from GMSPO.

Refer to the Hydra-Matic 4T60 (ME9) Automatic Transaxle Unit Repair Table of Contents for control valve assembly service information.

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.

Areas other than the designated high altitude counties listed in Figure 8.

A harsh 3-2 shift at low altitude 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.

3 - 2 Control Valve Spring Transaxle Model Identification Package Number Refer to Figure 1 --------------------------- ------------------------------ 8646980 OAAH, OABH, OAFH, OANH, OATH, OKCH, OKDH, OKPH, OKRH, OKLH 8662932 OAJH, OKHH 8646953 9AAH, 9ABH, 9AFH, 9AJH, 9ANH, 9ATH 8675936 9ACH, 9ADH, 9AHH (Use all components in package except labels)

Parts are currently available from GMSPO.

Refer to the Hydra-Matic 4T60 (ME9) Automatic Transaxle Unit Repair Table of Contents for control valve assembly information.

A 3-2 shift maneuver is obtained by allowing the vehicle to coast down to 17-20 mph (with closed or zero throttle) and then stepping into the throttle to obtain a 3-2 shift.

At start of production (SOP) 1987 an orifice pipe was added between the 1-2 servo release cover plate and the 3-2 coast down valve to allow a smoother second gear apply. Refer to Figure 6. The four new parts installed as a set will service certain past model transaxles with a harsh 3-2 shift maneuver condition.

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

Parts are currently available from GMSPO.

Refer to the Hydra-Matic 4T60 (ME9) Automatic Transaxle Unit Repair Table of Contents for appropriate service information.

If the new pump body assembly has a "one terminal" third clutch switch, remove it and replace with the "two terminal" third 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 IV of this bulletin. - Also, ensure the 3-2 control valve and 1-2 servo control valve move freely in their bores.

Service Procedure:

A coast down bump is obtained by allowing the vehicle to coast down 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 coast down bump may be caused by the 1 - 2 servo cushion spring. Refer to Figure 7. 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.

IMPORTANT- The 9ACH, 9ADH and 9AHH models could also have a harsh park/neutral to drive engagement bump. The suspect units were built from March 17, 1989 (Julian Date 076) to May 4, 1989 (Julian -Date 124) for these three models only.

P/N Description --- ----------- 8668123 1-2 Servo Cushion Spring (559)

Parts are currently available from GMSPO.

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

Refer to Figure 8 for designated high altitude counties.

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:

(1) Vacuum Modulator Assembly (1) Modulator Valve (1) O-Ring Seal (1) Spacer Plate (5) Gaskets (1) Cup Plug (Orificed) (2) Instruction Sheets

Service Package Transaxle Model Identification Number (Refer to Figure 1) --------------- ------------------------------ 8646966 6AAH, 6ACH, 6AFH, 6AMH 5AF, 5AM 8646967 6ADH, 6ARH

Parts are currently available from GMSPO.

A new vacuum line from the engine to the vacuum modulator MUST also be installed when using the service packages listed previously

P/N Vehicle Application --- ------------------- 1643771 DeVilles and Fleetwoods 1641441 Eldorados and Sevilles

Parts are currently available from GMSPO.

Please refer to appropriate Labor Operations for applicable years.

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.