NO 3RD GEAR (NEW THRUST BEARING)

Model and Year: 1984-89 "A" CAR WITH 440-T4 TRANSMISSION

TO: ALL CHEVROLET DEALERS

This bulletin covers a new Thrust Bearing Assembly (803) which replaces the Input Shaft/Sun Gear Thrust Washer (628) and Lock Up Sleeve (690) (see Figures 2 and 3). The Thrust Bearing Assembly will minimize friction. Under some operating conditions, friction may result in excess heat damaging the Thrust Washer (628) and melting the plastic shoes of the 3rd Roller Clutch Assembly (644). If the plastic shoes melt, the rollers will not be held and the loose rollers will cause failure of the 3rd Roller Clutch (causing no 3rd Gear). For this change to be implemented the following parts were modified:

- Input Housing and Shaft Assembly (626) mating surface for the new Thrust Bearing (803) has been reduced 0.9mm (0.03") to make room for the new bearing. The Lock Up Sleeve is not needed anymore and is eliminated.

- The 3rd Roller Clutch Dam (696) I.D. has been opened up 6.5mm (0.26") wider and the lip eliminated to accomodate the new Thrust Bearing Assembly (803).

- The 3rd Roller Clutch Cam (643) has been made 0.96mm (0.04") thinner to accomodate the increased thickness of the new Thrust Bearing Assembly (803). The edge of the 3rd Roller Clutch Cam (643) that faces the new Thrust Bearing Assembly (803) now has a squared off edge. This is for more contact area with the rollers since the cam is now thinner but the rollers stayed the same length.

SERVICE ACTION:

Packages listed under "Service Parts Information" are available to update past models (pre-1989) with the new Thrust Bearing and associated components and to service early 1989 models.

NOTE: The Input Shaft/Sun Thrust Washer and Lock Up Sleeve will NO longer be available for service from GMSPO for 1987 through 1989 models, replace worn components for these model years with the new Thrust Bearing and associated components. For 1986 and prior model years, use the new Input Housing and Shaft Assembly package for distressed 3rd Roller Clutch and/or Input Thrust Washer concerns, otherwise replace with previous parts that will still be available from GMSPO.

For a distressed 3rd Clutch Assembly, locate and correct the cause of the concern. This could be leaking Input Shaft Oil Seal Ring(s) (624) or a dislodged Shaft/3rd Clutch Spring Return Snap Ring (639) causing a dragging 3rd clutch pack. Replace the Snap Ring with a new one if it was found to be dislodged.

Also, inspect the Input Clutch Sprag Assembly (653) and Input Sprag Outer Race (654) for damage. This damage could be caused by the customer putting the transaxle in Drive 2 (D2) after a 3rd Roller Clutch Assembly (644) failure (no 3rd gear) so the car will travel at highway speeds causing excessive overrun speeds for the Sprag.

Important: Perform the Input Housing End Play Measurement when installing the new parts to assure proper end play. Reference Figure 4 for proper assembly of critical lubrication passages for the Sprag and Roller Clutch.

DATE OF PRODUCTION CHANGE: (Figure 1) -------------------------- The new Thrust Bearing Assembly and associated components were used in production on all models starting November 28, 1988 2nd shift (Julian Date 333).

SERVICE PARTS INFORMATION:

Part No. Description Package Contents Model Yr./Usage -------- ----------------------------- --------------- 8662970 Package - Input Hsg. and Shaft 1989 All Asm. Housing and Shaft Asm. Input Bearing Assembly, Thrust Roller Assembly Complete, 3rd Clutch Instruction Sheet, Input Thrust Brg.

Parts are currently available from GMSPO.

8662975 Package - Input Hsg. and Shaft 1984-88 All Asm. Housing and Shaft Asm. Input Bearing Assembly, Thrust Roller Assembly Complete, 3rd Clutch Instruction Sheet, Input Thrust Brg.

Parts are expected to be available (for part number 8662975) on 4/10/89. Until then normal part orders will not be accepted by GMSPO. Only verifiable emergency VIP orders will be accepted. SPO will make every effort to obtain parts. All parts will be placed on 400 control to waive VIP surcharges. However, the part will be shipped premium transportation at dealer's expense. All other order types will be cancelled as incorrectly ordered while the 400 control is in place.

IMPORTANT: Do not interchange parts from the two packages. The parts look similar, but have different dimensions.

SERVICE MANUAL REFERENCE:

Refer to the appropriate Service Information Manual, Section 7A1 Automatic Transaxle On Car Service and THM 440-T4/HYDRA-MATIC 4T60 or F-7 (ME9) Automatic Transaxle Unit Repair Section.

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.