here is one way to do it. pull plug with 2 vacume hoses running to the tps. be careful, its plastic. tps is the black thing attached to the injection pump on the passenger side. leave it off and go for a short drive. transmission should not shift until rpm gets close to redline. it will make a forced shift to second and then high. if you still have all your gears then you need to adjust your tps for less vacume. hook vacume connector back up, loosen the 2 screws and rotate the body of the shift actuator in the opposit direction. tighten and go drive, see what changes. it should shift later. adjust for your personal preference. if your truck shifts to soon you have plenty of vacume.