A/T - THM 440-T4 Loss of Drive and Reverse
88cad01
Bulletin No. T-88-101
File in Group 7
Number 185
Corp. Ref. No. 677136
Date March '88
SUBJECT: INTERMITTENT OR COMPLETE LOSS OF DRIVE AND REVERSE THM 440-T4
MODELS AFFECTED: 1985-1986 DE VILLES AND FLEETWOODS
1986 ELDORADOS AND SEVILLES
This bulletin supersedes Cadillac Serviceman Bulletins T-87-67 and T-86-16, Group 7, which should be destroyed.
FIGURE 1 - THM 440-T4 TRANSAXLE IDENTIFICATION INFORMATION:
Some 1985-1986 DeVilles and Fleetwoods and 1986 Eldorados and Sevilles equipped with a production transaxle built prior to April 1, 1986 (Julian Date 091) or a SRTA built prior to May 1, 1986 (Julian Date 121) may experience intermittent or complete loss of drive and reverse, refer to Figure 1 for Julian Date location.
This condition may be caused by rollover of the input sprag clutch assembly. Before proceeding with this repair, check for proper line pressures (refer to the appropriate Service Information Manual for specifications and diagnosis procedures).
FIGURE 2 - SPRAG & ROLLER CLUTCH FUNCTIONAL CHECK:
FIGURE 4 - INPUT SPRAG CLUTCH AND INPUT CARRIER ASSEMBLY CHANGES:
For vehicles with proper line pressures, sprag rollover can be repaired in either of two ways:
A. Sprag clutch replacement with original design components.
B. Updating the transaxle to the new design wider sprag clutch assembly and related components, refer to Figures 2 and 4.
NOTE: Option B will minimize potential recurrence of the condition but does require additional component updates and cost. Warranty repairs should follow service Option B or may be serviced with a current SRTA unit, depending on cost of repair.
FIGURE 2 - SPRAG & ROLLER CLUTCH FUNCTIONAL CHECK:
Service Procedure
1. Remove the transaxle from the vehicle and disassemble it to the point of removing the input sprag clutch assembly (653). Complete disassembly of the transaxle is not always necessary if there is no metal debris contamination.
2. Bench check the operation of the sprag and third roller clutch assembly as shown in Figure 2.
FIGURE 4 - INPUT SPRAG CLUTCH AND INPUT CARRIER ASSEMBLY CHANGES:
3. Inspect the sprag clutch assembly (653) for:
^ mispositioned sprag elements
^ broken ribbon tabs (between the sprag elements)
4. Disassemble the input sprag clutch assembly (Figure 4) and inspect for:
^ cracked inner or outer races (650, 654)
^ indentation marks on the inner race (650, indicates sprag element "rollover")
Replace the input sprag clutch assembly if any of the above conditions are present. Use the appropriate service part(s) referred to in the following "Service Parts Information" section.
Service Parts Information
SERVICE OPTION A:
To replace an original sprag clutch assembly with the same original design, use the following service part number:
PN Contents
8646986 1 - Input sprag clutch assembly
2 - Snap rings
1 - Input sprag clutch outer race
1 - Input sprag clutch inner race
2 - Input sprag clutch wear plates
FIGURE 3 - LUBE DAM WITH ASSOCIATED PART CHANGES:
SERVICE OPTION B:
To update a transaxle built with the original design sprag clutch to include the new (wider) input sprag clutch assembly, the transaxle must have the following three new design parts, refer to Figure 3. These parts are required if the transaxle was built prior to the Julian Dates listed:
1. P/N 8658368, lube dam (item 695) in production as of March 6, 1985 Julian Date 065)
2. P/N 8658407, final drive sun shaft (item 669) in production as of February 19, 1985 (Julian Date 050). Counter bore added to assemble with lube dam.
3. P/N 8658408, output shaft (item 565) in production as of February 19, 1985 (Julian Date 050). Chamfer removed to assemble with lube dam.
NOTE: These three parts must be installed to ensure proper lubrication of the third roller clutch and input sprag assemblies after updating.
With the above parts assembled in the transaxle, the new design input sprag clutch update service package listed below, may be used:
P/N Contents
8662906
1 - Input sprag clutch assembly (wider)
2 - Snap rings
1 - Input sprag clutch outer race (wider)
1 - Input sprag clutch inner race (wider)
1 - Input sprag clutch retainer (narrower)
1 - Input sun gear spacer (wider)
1 - Input carrier assembly complete (narrower hub)
Refer to the THM 440-T4 Automatic Transaxle Unit Repair Table of Contents in the appropriate Service Information Manual for input sprag clutch assembly service information.
For warranty purposes use Labor Operation T6193 at 7.2 hours.