A/T - 440T4 Converter Clutch Shudder

TSB 89-9 (Apr)

SUBJECT: HYDRAMATIC 4T60/440-T4

The ATRA Helpline has been plagued with calls on converter clutch shudder on the THM 440-T4. There have been a number of bulletins produced on this problem, to date. Some fixes solve some problems, but can create others.

Installing a heavier spring and/or a check ball in the converter clutch regulator valve may correct a shudder, if the problem is "not enough apply pressure, due to leakage in the converter or transmission, a severe converter clutch application can occur.

One major area of excessive converter pressure loss is the bushing in the hub of the converter, and the problem is more likely on a new bushing.




Increasing the apply pressure may not correct the shudder if there is too much converter or transmission leakage. It has been our experience that increasing the volume of apply oil to allow for the excessive leakage can be done without necessarily creating a harsh engagement. This can be done by grinding the 2nd land off the pressure regulator valve and allowing more oil flow into the converter (See Figure A).

To determine shaft-to-bushing clearance:

Find a sheet of paper that "mikes" at a thickness approximately .003. Cut a strip about 4" long and 1/4" wide.

Place the strip of paper inside the converter hub, with one-half folded on outside over hub.

Install a good 125C, or a 440-T4 drive sprocket support (stator support) shaft into the converter.

If you are unable to install the support shaft into the converter, without excessive force, your clearance is less than .0015

If you are able to install the drive support sprocket shaft into the converter, without excessive force, the clearance is more than .0015 and excessive leakage will occur.