With a manual valve body, if you put it in D you start out in 3rd. Put it in 2nd you start out in 2nd. With a stock valvebody, D goes 1st to 2nd to third. Stock valvebody, put it in second, it starts in second. Leave it in second and floor it, it will shift to 3rd when the rpm's get to a certain point even though you have the selector in 2nd. Thats where a manual valve body works great. If you leave the man. in 2nd for compression braking, it will stay in 2nd.