Oops. While the MT643 is indeed a nice transmission, the MD3060 is the one I want. MT643 is a mechanical control type 4 speed with 3rd and 4th locking. MD3060 is a larger, electronic controlled 6 speed which apparently locks on all gears. This is good news as MD3060 seems to be very popular compared to trying to locate the MT643. Only real drawback is electronics control adds a bit of cost, especially if it breaks.