August 01, 2019
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.