Symptoms:

  • Premature clutch wear
  • Inability to alter clutch apply pressure curve

Cause:

OE valve and spring configuration do not allow TCM pressure control strategy to adequately raise clutch pressure and shorten shift durations.

Correction:

This Sonnax kit alters the trim valves and springs, resulting in a more responsive clutch pressure.

1000/2000/2400

Trim Valve & Spring Kit
Part No. 37000-12K

Fits '00-'09 units only. The F-trim spring is applicable to '00-'05 valve body casting only.


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The OE trim valve and spring configuration has a very conservative pressure curve, resulting in premature clutch wear in heavy-duty Allison® 1000/2000/2400 ('02-'09) applications. Clutch damage occurs when the TCM pressure control strategy is unable to adequately raise clutch pressure and shorten shift durations. Sonnax trim valve and spring kit 37000-12K includes A-, B- and F-trim valve springs and a A- and B- trim valves with recalibrated valve ratios, which is the only way to predictably improve clutch pressures and apply rates, resulting in more responsive clutch pressure (see Figures 2 and 3).The F-trim bore in '00-'05 units contains an F-trim sleeve (Figure 1). This bore can be upgraded using the spring in this kit and Sonnax F-trim valve sleeve 37000-03.

  • 15% More clutch pressure & clamping force than OE
  • Firmer and shorter upshifts
  • Firmer TCC engagement
  • Improved engine braking on deceleration
  • A-Trim Valve & Spring
  • B-Trim Valve & Spring
  • F-Trim Spring
  • 1000/2000/2400 Trim Valve & Spring Kit 37000-12K
  • 1000/2000/2400 Trim Valve & Spring Kit 37000-12K
  • 1000/2000/2400 Trim Valve & Spring Kit 37000-12K details
  • 1000/2000/2400 Trim Valve & Spring Kit 37000-12K details
  • 1000/2000/2400 Trim Valve & Spring Kit 37000-12K details