Original 1969 Riviera with TH400 3 speed. The manual says that L2 and L1 may be used when going down a hill which helps braking the car. Is it okay to use L2 and L1 for take off (race the car) and shift manual to drive or is it not designed for this originally? When i take off part throttle in L2 it shifts stronger/faster between the gears. Thanks.