NEW FINAL DRIVE ASSEMBLY FINAL DRIVE SUN GEAR SHAFT

TRANSMISSION APPLICATIONS: SUBJECT: ------------------------- ------- 1988 THM 440T4 (ME9) NEW OUTPUT SHAFT; FINAL DRIVE SUN GEAR; AND FINAL DRIVE ASSEMBLY

TRANSMISSION MODELS: VEHICLE APPLICATIONS: ------------------- -------------------- All 1988 A,C,E,H, AND W CARS

(Revised to correct typing error)

Bulletin Covers:

A new final drive assembly (679), output shaft (565) and final drive sun gear shaft (669) for some 1988 A, C, E, H and W Cars equipped with a THM 440-T4 transaxle. The new final drive assembly (679) has larger differential side gears (688) and larger differential pinion gears (686)(refer to Figure 2). To accommodate the larger gears, the output shaft (565) was lengthened by .73mm (.029"). The final drive sun gear shaft (669) was also changed by adding two additional lube holes for increased lubrication to the final drive.

DATE OF PRODUCTION CHANGE:

April 6, 1988 (Julian Date 097) for all THM 440-T4 transaxles using a 3.33 ratio final drive assembly; May 5, 1988 (Julian Date 126) for all THM 440-T4 transaxles using a 3.06 ratio final drive assembly, and June 10, 1988 (Julian Date 162) for all models using the 2.84 ratio final drive assembly.

During May, 1988 the transaxle I.D. nameplate was also changed to provide for easier model identification (refer to Figure 1). The changes to the nameplate were:

- larger letters designating the transaxle model - eliminated the "8" (designating 1988 model year) and "H" (designating THM 440-T4) on right hand side of tag.

SERVICE ACTION:

When servicing a 1988 THM 440-T4 transaxle use the parts listed in the Service Parts Information section below. DO NOT attempt to mix these three components with parts that look similar or the following misbuilds will occur:

o Excessive clearance between the end of the output shaft and the differential pinion shaft if the new output shaft is assembled with the previous final drive assembly.

o The output shaft snap ring cannot be installed if the new final drive assembly is assembled with the previous output shaft.

o Insufficient lubrication to the final drive assembly if the previous final drive sun gear shaft is assembled with the new output shaft and final drive assembly.

SERVICE PARTS INFORMATION:

Part No. Description -------- ----------- 8661905 Package, Final Drive (3.06 final drive ratio) 8662922 Package, Final Drive (3.33 final drive ratio) 8662923 Package, Final Drive (2.84 final drive ratio) 8661089 Shaft, Output 8661020 Shaft, Final Drive Sun Gear

SERVICE MANUAL REFERENCE:

Refer to the THM 440-T4 (ME9) Automatic Transaxle Unit Repair section in the appropriate Service Manual.

SERVICE NOTES:

Additional ways to identify a transaxle with the new final drive assembly are:

(1) the output shaft has a dab of light green paint on the end (Figure 3), and (2) the differential pinion shaft (683) is black (Figure 2).

Refer to the chart below for Julian Date information, final drive ratios and transaxle model information:

Final Julian Drive Date Ratio Transaxle Model Code Car Line Engine ------ ----- -------------------- -------- ------ 162 2.84 BYH E 3800 FCH A-Wagon Export 3.8L FSH C & H Export 3.8L

126 3.06 BKH C & H 3800 FBH H 3.8L

097 *3.33 CFH, CMH, CWH, CXH A 2.8L CRH,CTH W 2.8L BJH H 3800 BRH E 3800 BTH C & H 3800 FJH H 3.8L

* All 1988 AAH, ABH, AFH, ANH and ATH model THM 440-T4 transaxles use the 3.33 ratio final drive assembly and were assembled with the new components described in this bulletin.

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.