FAQs – TCRA, Torque Converter Rebuilders Association

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Non-Member FAQs

I have recently come across several GM 300mm TM BX converters with out the small bleed holes in the pistons. One was a 2006 the other a 2004. Will these interchange with older models & vise versa?

The .028” orifice was added to the clutch for extra cooling. General Motors found that the cooling the .028” orifice added did not offset the lose of clamping force, and the orifice has been eliminated from most models. You will be better off without the orifice in all pistons.

We recently sent a 4T65E (9YFB) trans to a customer & it called for a 245mm converter code FLQB. When the trans core was returned the converter was a 258mm converter, code JSFM. I looked up a 4T65E (8YFB) & it calls for the 258mm JSFM converter. Will these converters interchange?

The stator and turbine shafts on the 4T65E transmissions are longer than the stator and turbine shafts on the 4T60E transmissions and are not interchangeable. Generally the 245mm converters are used with 4-cylinder engines and the 258mm converters are used with 6-cylinder engines. The FLQB was replaced by the 258mm series converters, and they were both being used by General Motors in the same year. The key for driveability is to replace the converter with what came out of the vehicle.

What would be the result of machining the stator blades off the impeller side of the stator? Would there be any adverse side effects?

In hopes of lowering the stall of the converter, machining down the impeller or primary pump side of the stator would open the window-area of the stator and lower the stall; however, this can be a significant trial and error procedure. Another troubling side effect: cutting torque multiplication. Lowering this limits the amount of power, and it could make the vehicle feel sluggish at takeoff. Another suggestion, bend the blade closest to the inner diameter toward the stator. This will decrease the impeller to turbine clearance.

How would I go about correcting a cracked hub for a converter from a JCB forklift using a PS 750 5-speed powershift transmission?

Easy fix: Purchase a replacement unit from Sonnax. If you’re not interested in buying a replacement, or simply cannot sacrifice the time, you can machine the weld off and reweld the TC with a better weld and drop a bead of weld on the inside of the machined flat. Just don’t use a hot weld in fear of distorting the weld.