1989 MODEL YR. PRODUCT CHANGES HM-290/HYDRA-MATIC 5LM60

TRANSMISSION APPLICATIONS: SUBJECT: 1989 HM-290/HYDRA-MATIC 1989-1/2 MODEL YEAR PRODUCT CHANGES 5LM60 (RPO MCO,MG5)

TRANSMISSION MODELS: VEHICLE APPLICATIONS: ALL 1989 C/K TRUCKS

Bulletin Covers:

Changes made for better manufacturing processes and product serviceability.

Change - New output shaft bearing assembly (33). The new bearing is thinner and serviced only as a sealed unit (Figure 1).

Reason - Serviceability and better resistance to contamination.

Change - New output shaft (23/24) (Figure 1).

Reason - Dimensional changes needed to accomodate new bearing, threaded thrust ring elimination.

Change - Threaded thrust ring assembly (39-42) eliminated (Figure 1).

Reason - New design has better serviceability, saves material.

Change - New reverse idler shaft assembly (46) eliminates 2 needle bearing assemblies (50), 4mm ball (40) and 0-ring (52) (Figure 1).

Reason - New design has better serviceability, saves material.

Change - New rear housing (300) (Figure 2).

Reason - Dimensional changes needed for new output and reverse idler shafts, reverse idler shaft bore eliminated, revised bore location for new speed sensor (2WD only).

Change - New speed sensor (2WD only) (314) (Figure 2).

Reason - Revised location requirements.

Change - New shift shaft select bias system (229-237) eliminates 5th and reverse detent assembly (204, 239-241, 247-248) and bore in front housing (200) (Figure 2).

Reason - Improved shift feel.

SERVICE NOTES:

Except for eliminated parts, assembly and disassembly procedures for the HM-290/HYDRA-MATIC 5LM60 are unchanged.

DATE OF PRODUCTION CHANGE: (Figure 3) ------------------------------------ The changes listed above were implemented January 7, 1989 (Build Date A 07) for C-Truck applications (2WD) and January 11, 1989 (Build Date A 11) for K-Truck applications (4WD).

SERVICE PARTS INFORMATION:

Refer to the following list for part information when servicing a HM-290/HYDRA-MATIC 5LM60 built after the dates listed above. Refer to current CANSPO catalogue when servicing previous units.

Do not mix previous and new parts--the unit will not assemble properly.

APPLICATION PART NO. PART NAME C K ------- --------- ------------ 8672318 Shaft--Output (23) x 8672315 Shaft--Output (24) x 8672210 Bearing Asm--Output Shaft (33) x x 8672200 Shaft--Reverse Idler (51) x x 8672201 Bearing Asm--Needle Reverse Idler (50) x x 8672202 Gear--Reverse (49) x x 8672203 Washer--Thrust (48) x x 8672282 Housing Asm--Rear (300) x 8672285 Housing Asm--Rear (301) x 8672317 Housing Asm--Front (200) x x 8672237 Speed Sensor--Internal Trans (314) x 8672244 Lever Asm--Shift Shaft (229) x x 8672248 Spring--Bias Load Torsion (234) x x 8672247 Support--Bias Spring (237) x x 8672207 Rotor--Speed Sensor (45) x

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.