Throttle pressure or kick-down linkage has to be connected to increase internal hydraulic pressure in transmission when car accelerates. Early soft shifts, slippage and heat is the result of low transmission line pressure by incorrect adjustment or lack of kick-down linkage; this condition will burn up all friction surfaces on bands, and clutches in short order.
Not only get the linkage from donor car, but grab the little lever all that rigging connects to on the transmission as well.
