the lentech valve body changes the shift pattern from a 1-3-OD, to a 1-2-3/OD pattern so that you can use second gear manually if you so choose without using the aod dance(start in first shift to third, and then back to first) which causes damage to the transmission internals. the inner input shaft can be delicate when the majority of power is run through it, but the valve body also changes that routing also. an upgraded inner input shaft is still recommended. one more thing, lentech also builds a full pressure valve body so you can use the throttle valve cable as a kick down cable rather than controlling the valve body pressure. that way you dont have to get the tv cable adjustment right.