Brad at Columbus Trans (no login) Posted May 4, 2012 5:10 PM
Your solenoid reg valve is sticking in the bore when it gets hot. The vehicle will work fine cold as the valve is in the relaxed position. Once a set of shifts has been made and the valve is stroked, it will seize in the bore. This is because the slight wear in the bore, swelling from heat, and the balance pressure cause just enough resistance to overcome the spring. This is why it clunks coming out of 4th (reg pressure is incorrect). The bigger issue is that the pressure on the solenoid b circuit will build and stroke the 2-3 shift valve ever so slightly. Since 3rd requires the forward clutch to disengage, the forward clutch pressure is bled off on the other side of this valve... resulting in a neutral at a stop that will slam into gear repeatedly. Sonnax offers a resizing kit and an upgraded valve to correct the problem. or you could try another valve body. Careful not to mix early and late designs due to an epc tcc balance hole in the plate, and a regulated plunger under it in the tcc valve. Enjoy.