THM 3T40 (125C) - Pump Rotor And Slide Changes

CHANGE: Beginning in late 1985, the dimensions of the pump rotor and pump slide changed (See Figure 1).

REASON: Improved pump capacity.

PARTS AFFECTED
(1) PUMP ROTOR - The outside diameter of the rotor was made smaller. The previous rotor O.D. was 2.235", and the present rotor O.D. is 2.210". (See Figure 1).
(2) PUMP SLIDE - The height of the pump slide stop was made shorter. The previous pump slide stop measures .426", and the present pump slide stop measures .406" (See Figure 1).

INTERCHANGEABILITY:
The pump rotor and pump slide are interchangeable. "ONLY AS A SET". You CANNOT mix these parts.
(1) If you install the previous (Large) rotor with the present (Short) slide, interference will result and usually strip the rotor splines.
(2) If you install the present (Small) rotor with the previous (Tall) slide, erratic line pressures can be encountered.
(3) DO NOT MIX THESE PARTS.
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SERVICE INFORMATION:

THM 4L60-E - LACK OF LUBRICATION

COMPLAINT: Vehicle is brought to your shop and has failed because of lack of lubrication. You check the cooler or possibly replace the cooler as a precaution. After replacing the necessary failed parts, the vehicle is returned with the same problem.

CAUSE: The cause may be, a defective pump cover (Stator) from the factory, that was not drilled completely through the "Lube From Cooler" passage, as shown in Figure 1. If this passage is not drilled through, there will be no lubrication to the rear of this unit as all lube must pass through the pump cover (See Figure 1). Every one that we have encountered, and we have seen several, had been drilled just deep enough that the cup plug that seals this passage after drilling was installed in the cover.

CORRECTION: Replace the pump cover as necessary with a new one and inspect every one that enters your shop to ensure no return failures. All of the pump covers we have seen at this point, were the 13 vane variety. Find more useful tools like Lexia 3 PP2000 and digimaster 2 to solve the car problems.