I was under the impression it was shifting, rather than slipping, but I may be misreading the OP's description.

Slipping is another whole kettle of fish, and such a load of aggravating fun to troubleshoot... I finally coughed up for the incredibly expensive ($25.00 gasp!) manual from ATSG that lets me see what all is going on in there, and was amazed just how much you can find out just by knowing what *should* be working at what point.

But as you say, no relation between slipping shifts and the kickdown switch.

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-Josh
Testing the cheap Mercedes axiom, one bolt at a time...