THM 440-T4 – CENTER GEARBOX DISTRESS (LUBE CHANGES)

COMPLAINT: Repeated failure of the 3rd roller clutch and/or the input sprag.

CAUSE: Lack of lube oil to 3rd roller clutch and input sprag. Find more obd2 code reader for hlep?

CORRECTION: Modification as follows, of the parts indicated, will increase lube flow to both the 3rd roller clutch and the input sprag.

1 . MODIFY OUTPUT SHAFT:
Grind four (4) flats on the output shaft at the front of the bearing in the locations.

2. MODIFY OUTPUT SAHFT BEARING:
Remove idividual needle bearings, in three equally spaced locations around the bearing, to provide three “Troughs” for additonal lube oil to flow. Removing the needles does not impair the durability of the bearing assembly.

3. MODIFY ASSEMBLY PROCEDURE:
When installing the sprag assembly onto the input sun gear, align one of the three lube oil holes in the inner race, with one of the two lube oil holes in the input sun gear.

THM 4L60 (700-R4) HIGH LINE PRESSURE

COMPLAINT: Very harsh upshifts, all gears, harsh engagement forward gears and reverse.

CAUSE: High line pressure. The cause of the high line pressure can be a hung pressure regulator valve, or a binding slide in the pump body. The bind of the slide can be caused by mis-tightening the pump body to the pump cover. Another possible cause can be a blown orifice cup plug located in the pump cover shown in Figure 1. This cup plug is in the reduce pressure oil circuit.

CORRECTION: CORRECTION: The problem can be corrected by replacing the orifice cup plug. The orifice in this plug is .040-.045.

LUBE CHANGES

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THM 440-T4 LOCKS IN REVERSE

A 1984 through 1987 vehicle equipped with a THM 440-T4 transaxle may have an intermittent no reverse or locking in reverse condition un-til shifted to a forward range prior to shifting into reverse (“un-loading” the parking pawl). This condition may be caused by a “dent” on the parking paw1 that does not allow the paw1 to release until “un-loaded”. You can get more obd code scanners for help.

Date of Production Change: (Figure 1)
Effective May 1, 1987 (Julian Date 121) all 1987 THM 440-T4 transaxles were produced with parking paw1 assemblies not having a “dent”.

Service Action: (Figures 2 and 3)
If this condition is encountered, remove transaxle and replace the final drive internal gear/parking paw1 assembly (No. 673) and actuator guide, plunger and spring assembly (No. 709 – No. 711). Also inspect the parking gear for wear or damage and replace if necessary.

Service Parts Information:
Part Number                       Description
8656372                          Final Drive Internal Gear/Parking Paw1 Assembly
8656689                          Actuator Guide, Plunger and Spring Assembly
8644238                          Parking Gear

Service Notes: (Figure 2)
Before installing the replacement parts , inspect the new final drive internal gear/parking paw1 assembly to make sure it does not have a “dent”.  Some hot car tools like Launch CR-HD and SKT100 may bring you more information.