• Overheated transmission
  • Code P0741
  • RPM surge
  • TCC apply & release concerns


The F-trim valve is a highly active valve train known to lose hydraulic integrity and malfunction due to wear along the valve spool/bore wall, and on the sleeve I.D. and OD.


Restore proper hydraulic control by reconditioning the bore and replacing worn parts with the oversized Sonnax valve kit.


Oversized F-Trim Valve Kit
Part No. 37000-30K

Fits '00–'05 units only.

You need this if... View Instructions Find a Distributor

The F-trim valve in Allison® 1000/2000/2400 ('00–'05) units is controlled by a PWM solenoid that continuously oscillates the valve. When the valve and sleeve become worn from constant motion the TCC PCS pressure is allowed to cross leak, or escape to exhaust, inhibiting the valve from stroking against the spring and causing converter apply concerns, TCC surge, TCC slippage, code P0741 and overheating. When wear becomes severe it can cause the valve to stick, causing converter release problems as well as apply problems, dependent on where in the bore the valve sticks. Reconditioning the bore and installing Sonnax oversized F-trim valve kit 37000-30K replaces the entire valve train to restore F-trim valve function to normal operation.

  • Hardcoat anodized valve combats premature wear
  • Annular grooves on the valve help center it in the bore to reduce future side-load wear
  • Valve
  • Sleeve
  • Spring
  • O-Ring

Sonnax valve body layouts provide a detailed overview of individual units making it quick and easy to determine what’s available for the specific valve body you’re working on. See all Sonnax valve body layouts.

GM Allison® 1000/2000/2400 Valve Body Layout

GM Allison® 1000/2000/2400 Valve Body Layout
  • 1000/2000/2400 Oversized F-Trim Valve Kit 37000-30K
  • 1000/2000/2400 Oversized F-Trim Valve Kit 37000-30K

You need this if...

Vacuum testing at the port(s) indicated fails to hold the recommended minimum in-Hg, or if wear is visually detected.

1000/2000/2400 Oversized F-Trim Valve Kit Vacuum Test Locations