Transgo shift-correction kit for the 6-speed Allison 1000/2000/2400 (2005-2009) that firms up shifts and raises line pressure to stop clutch slip under tune and towing.
This is the Transgo SK Allison-Jr kit for the six-speed Allison 1000, 2000, and 2400 automatics used behind the 6.6L Duramax in 2005 through 2009 GM 2500 and 3500 trucks (LLY, LBZ, and LMM). It is a valve-body reprogramming kit, not a full rebuild kit: it recalibrates how the transmission applies its clutches so the unit holds power instead of slipping it away.
The Allison six-speed leaves the factory with soft, comfort-tuned shifts and modest line pressure. Add a tune, bigger injectors, or a loaded trailer and the C1, C2, and other clutches start slipping on the 1-2, 2-3, and 3-4 apply, which glazes frictions and eventually burns them. This kit re-springs the pressure regulator and shift valves and drills a calibrated feed passage (the drill bit is included and sized in the instructions) to raise working pressure and crisp up the apply so the clutches lock instead of slide.
What is in the box: the machined valve body springs and accumulator piston, the piston pressure regulator valve, a new gasket, the drill bit, and step-by-step installation instructions. It installs with the pan and valve body off on the bench; no transmission removal is required. Fits the 6-speed 2005-2009 units only, not the earlier 5-speed 2001-2004 boxes.
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