How To Tell If Your Transmission Pump Stator Is Broken Or Spun (And What To Do If It Is)

In most automatic transmissions, the torque converter is mated to the pump of the transmission in two places: the input shaft and the stator (also called a stator tube or stator support).

What is it and what does it do?
This splined piece of steel centers the torque converter into the pump, provides lubrication circuits within the pump, and can also stabilize and support the input shaft in some setups. In many OEM applications, such as the powerglide and TH400, the tube is pressed into the pump casting. In high horsepower and torque setups, the stator in the torque converter is receiving tremendous amounts of pressure from the power generated by the engine. This heavy load is placed onto the pump's stator tube.

If this component fails, it will often turn or twist within the pump casting. A visual inspection of the pump's exterior will not indicate any failure. However, the function of the transmission and torque converter can be greatly affected. If your transmission and torque converter have suddenly changed their performance profiles, check the stator tube during a full disassembled inspection to make sure this sometimes overlooked component is operating properly.

What can happen?
1. Changes in torque converter stall speed and operation
2. Extreme heat generation in transmission and torque converter
3. Failure of transmission clutches, bands, and overall performance issues

A spun or broken stator tube can be replaced with an aftermarket version (like the one pictured above). Made from chromoly steel, this is a big improvement over the OEM tubes. However, the tube is still pressed into the pump body, which can fail again in some situations.

The best solution for a racing car or truck is a completely aftermarket pump like our high volume powerglide pump, which features a bolted-in stator support tube. This tube is virtually unbreakable in even the most stressed combinations such as Pro Mod and Monster Truck class racing.