ive read a few posts about this happening but i dont understand it.

It has speed sensors (3) that monitor the rpms different places inside the trans. This info is monitored by the TCM (computer). With this info the computer is able to see clutch slippage. There are a couple of trim solenoids in the valve body. They adjust clutch apply speed and pressure... not sure if they do both.

Anyway, the computer adjusts these solenoids all the time based on component rpm differences and I'm sure a bunch of other input.

It's got a pre-mapped table of parameters that are supposed to be "perfect" shift parameters at different rpms and power levels. It compares the "perfect" parameters with actual data recieved from the sensors and the ECM (engine computer) and adjusts the trim solenoids to try and match the target map.

Timing of clutch application and engine rpm is critical if you want smooth shifts. Because of the raw design of the Allison, computerization is almost the only way it can work. It's crude (simple) mechanically but very advanced electronically.

Sudden power changes will fool it for a while causing soft or hard shifting depending on what it was used to.

Hopefully some of the experts will clarify my rendition.

moving to Allison OEM forum.. please post in correct sections for best exposure and best feedback. Thanks