A/T - 440T4 Converter Regulator Spring Update

TSB 89-17 (June)

REVISION OF: 88-21

SUBJECT: Converter regulator spring

Hydra-matic 4T60/THM 440-T4




When servicing the THM 440-T4 transmission, it is recommended that you replace the converter regulator valve spring (See Figure 1) with a spring that has a tension of 2-1/2 to 4 pounds.

This will raise converter charge pressure in the torque converter and reduce the possibility of converter clutch shudder.

Many of the transmissions built after mid-1985 have no spring on this valve, and a 2-1/2 pound spring should be installed.




To weigh the spring, compress the spring with the valve on a scale until the stem touches the scale, then read the scale (See Figure 2).

A spring removed from an ATX direct or intermediate return spring assembly has a tension of about 3-1/2 pounds.
Shift valve springs from C-4 and C-6 valve bodies are also close to the correct tension.

Do not use a spring heavier than 4 pounds, or block the valve to the maximum position. This will result in harsh converter clutch engagement, or re-engagement after coast.