NEW PROCEDURE FOR REPLACEMENT OF FINAL DRIVE PINION

MODELS AFFECTED: 1982-1988 CIMARRONS 1985-1989 DE VILLES, ELDORADOS, AND SEVILLES

A new service procedure has been developed to replace final drive pinion gear washers and the differential carrier sun gear bearing on vehicles equipped with the THM 440-T4/Hydra-Matic 4T60 or THM 125C/Hydra-Matic 3T40 transmissions. SERVICE PROCEDURE

Checking End Play:

Measure pinion gear end play using a feeler gage. Refer to Figure 1. The correct end play range is 0.24mm-0.63mm (0.009"-0.025"). If out of range, follow the procedure given in this bulletin. (It is not currently included in the unit repair section of the Service Information Manual.)

Disassembly:

1. After removing final drive from unit, clean the entire bottom pan since it will be used to hold needle bearings.

2. Using a screwdriver, remove the spiral snap ring (wear safety glasses). Refer to Figure 2.

3. Be careful when pulling out the pinion gear shaft (804) from pinion gear (refer to Figure 3) so needle bearings do not get lost. Put a mark on the gear with chalk or crayon so the gear can be installed the same way it was removed. OVERHAUL ONE PINION AT A TIME SO PARTS DO NOT GET MIXED.

4. Tilt final drive and remove the pinion gear (808), washers (806,807,809), and needle bearings. (Needle bearings will fall out of pinion gear. Use bottom pan to catch/hold them.) Refer to Figure 4.

5. Inspect washers, needle bearings, and pinion shaft for wear. Discard bronze washer (806) and replace with new steel washer (807) from service kit.

* If replacement of only the thrust bearing (refer to Figure 3) (677) 4T60, (676) 3T40 is necessary, use steps 1 through 3. After steps 1 through 3 are completed, move pinion gears to provide clearance to replace thrust bearing then complete steps 6 through 7 of assembly procedure.

Assembly:

1. After cleaning pinion gear apply Transjel, J-36850 assembly lubricant or petroleum jelly, to the inside of gear. (Do not use any grease or axle grease.)

2. Install square cut washer (809) onto pinion gear shaft (804). Insert the shaft and washer into gear so washer is flush with gear and shaft is 3/4 inside gear. Refer to Figure 5.

IMPORTANT: SQUARE CUT WASHER IS TO BE ASSEMBLED BETWEEN THE TWO ROWS OF NEEDLE BEARINGS!

3. Install needle bearings (805) one at a time into gear - 44 per pinion (22/row) for 3.06 and 3.33 ratios; 36 per pinion (1 8/row) for 2.84 ratio. Occasionally twist pinion shaft so needle bearings will line up and allow for all needle bearings to be installed. Refer to Figure 6.

4. Install two washers (807) into final drive assembly. Refer to Figure 7.

5. Install remaining two washers (807) on top of pinion gear. Refer to Figure 7.

6. Insert pinion gear and washers, in same position they were removed, into final drive. Check chalk or crayon mark.

IMPORTANT: SURE THE PINION GEAR IS INSTALLED THE SAME WAY THAT IT WAS REMOVED. IF THE GEAR IS INSTALLED UPSIDE DOWN, IT MAY CAUSE A NOISE BECAUSE OF THE CHANGE IN SET WEAR PATTERN.

7. Install pinion gear shaft (804) without dislodging needle bearings, and install spiral snap ring. Refer to Figure 7.

IMPORTANT: MAKE SURE THERE ARE NO EXTRA NEEDLE BEARINGS LEFT AFTER REPLACING WASHERS. THERE MUST BE NO SPACES BETWEEN NEEDLE BEARINGS. CHECK FOR PINION END PLAY.

DO NOT INSTALL MORE THAN THE REQUIRED AMOUNT OF WASHERS (FOUR PER EACH PINION, TWO ON EACH SIDE OF PINION) INTO THE FINAL DRIVE.

Service Parts Information:

Whenever ordering replacement parts for the final drive assembly, refer to the following part numbers:

Package Description P/N

1. Package: Pinion, Thrust Washers for 2.84 ratio final drive 8665957 16 steel washers (807)

2. Package: Pinion, Thrust Washers for 3.06 and 3.33 ratio final 8665958 drives 16 steel washers (807)

3. Bearing, Differential Sun Gear 8646254

Parts are currently available from GMSPO.

Service Information Manual Reference:

Whenever service and/or replacement to the final drive assembly is necessary, refer to the unit repair section of your Service Information Manual.

WARRANTY INFORMATION VEHICLE SERIES Operation Operation Description Number C D E J K V

Differential and Final Drive Assembly, K7620 6.7 7.3 6.7 7.3 Transaxle - Replace

Policy: MP

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.