PRELIMINARY DIAGNOSIS AND DESCRIPTION/NEW TRANSAXLE-4T60

VEHICLE APPLICATIONS:

1989-90 'W' CARS

(Revised to change bulletin #89-7440-111 to #89-7440-113) Bulletin Covers:

TRANSAXLE MODELS: OCHH, OCJH, OYKH, OYLH, OLAH, OLCH

CHANGE TO ASSEMBLY CCOMPONENTS: (Figure 1) ------------------------------ Five early 1990 HYDRA-MATIC 4T60/THM 440-T4 transaxle models require new Shift Speed and Oil Pressure Charts, Wiring Diagram and a vacuum modulator (turbo models only). Note: the OLCH model will be released during the normal 1990 new model introduction.

SERVICE MANUAL REFERENCE:

Reference the following information when servicing a 1990 model. All other instructions and procedures are the same as published in 1989 Service Manuals. Refer to the appropriate Automatic Transaxle Diagnosis section in the 1989 Service Manual for information not covered in this publication.

TRANSAXLE MODELS: OLAH, OLCH ---------------- SUBJECT: New Modulator Assembly For The 3.1L Turbo Engine

CHANGE TO ASSEMBLY COMPONENTS: (Figures 2 and 3) ----------------------------- The 1990 HYDRA-MATIC 4T60/THM 44OT4 transaxle modulator assembly, 1-2 accumulator spring package and the transaxle cooler connectors have been changed for the OLAH and OLCH models only.

SERVICE ACTION:

The transaxle modulator assembly was changed for the 3.1L turbo engine. The transaxle models, OLAH and OLCH use the standard non-aneroid vacuum modulator assembly (see Figure 2). Engine torque is maintained at high altitudes, therefore eliminating the need for an aneroid type modulator (see Figure 3). If an aneroid modulator (Figure 3) is installed on the OLAH or OLCH model, durability concerns may result.

The non-aneroid modulator load check is to be preformed with J 35258 while the aneroid modulator requires J 36619. Follow procedures outlined in the On Vehicle Section of your 1986 (for non-aneroid modulators) or 1989 (for aneroid modulators) Service Manual.

The 1-2 accumulator spring package has changed for the OLAH and OLCH models. A second spring (116) (Figure 4) has been nested, which provides a smooth apply of the 2nd clutch.

IMPORTANT: The Hydraulic Fluid Diagrams are not affected by this change except the 1-2 accumulator springs will be nested.

The cooler lines to and from the transaxle oil cooler in the radiator and the connectors installed in the transaxle case have been increased to 3/8 inch. This is for increased lubrication flow and cooling for the 3.1L turbo models, OLAH and OLCH.

TRANSAXLE MODELS: OCHH, OCJH, OYKH, OYLH, OLAH, OLCH ---------------- SUBJECT: New Shift Speed And Oil Pressure Charts ------- CHANGE TO ASSEMBLY COMPONENTS: (Figures 5 and 6) ------------------------------ The 1990 HYDRA-MATIC 4T60 transaxle shift speed and oil pressure charts have been changed for the new 3.1L engines.

SERVICE ACTION:

Reference the new shift speed and oil pressure charts when servicing a 1990 OCHH, OCJH, OYKH, OYLH, OLAH, OLCH models.

SERVICE MANUAL REFERENCE:

Reference the 1989 Service Manual for other information not contained in this bulletin.

TRANSAXLE MODELS: OCHH, OCJH, OYKH, OYLH, OLAH, OLCH ---------------- SUBJECT: New Wiring Harness to Prevent Pinched/Shorted Converter Clutch Solenoid Wires

BULLETIN COVERS: (Figure 7) --------------- A revised wire routing for the Torque Converter Clutch Solenoid (TCC) requires a new Wiring Harness. The TCC wires are now routed straight down from the Engine Wire Harness Connector to the TCC Solenoid instead of going around the Oil Pump Body. This change reduces the possibility of the TCC wires becoming pinched/shorted between the Pump Cover and the Case Side Cover Pan during assembly. For this change to occur, a Wire Conduit Clip, for the TCC solenoid has been added to secure the Wire Conduit (TCC).

SERVICE ACTION:

The new Wire Harness will not be available for service. Order the old style wire harness to service these new models. When using the old style wire harness ensure the routing will not allow the TCC wires to get pinched between the pump cover and case side cover pan during assembly. The new TCC solenoid wire conduit clip must be used with the new wire harness.

SERVICE PARTS INFORMATION:

When the supply of the old style wire harness indicated by the asterisk "*" is depleted, the new style wire harness will be available.

Part No. Description Model Year - Model Usage ------- ----------- ---------- ------------ *8662852 Harness Assembly, Wiring 1990 - OCHH, OCJH, OYKH, OYLH, OLAH, OLCH

8668271 Clip, Wire Conduit (TCC) 1990 -All

*Old style wire harness

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.