One further clarification to what CGW said.
There are basically three types of Mamiya 645 manual focus bodies.
1) The first generation older bodies, such as the 645, the 645J and the 645 1000s. None of these permit interchangeable backs (they do use the same inserts, however, as all the other bodies). There is a largish, heavy, slow and loud motor winder that works with at least some of these models;
2) The next generation bodies, namely the Super, the Pro and the Pro Tl. They all permit use of the new 645 interchangeable backs. The motor winder for the first generation bodies will not work on these second generation bodies. The Winder N and the WG401 (both of which use AA batteries) will work on all three second generation bodies. The instructions for WG402 (which uses 2CR5 lithium batteries) say that it will work with the Pro and Pro Tl bodies, but will not work with the Super bodies; and
3) The final generation body, the 645e (which was available concurrently with the 645 Pro Tl) went back to having a fixed, non-interchangeable back and prism. It was designed to work either with a normal manual crank winder or a "rapid winder" grip with a thumb advance (similar to a 35mm camera). Apparently there is undocumented compatibility between the 645e and the first generation bodies, at least to the extent that the largish, heavy, slow and loud motor winder that works with those bodies also will work with the 645e.
Hope this helps.
PS there is unfortunate confusion in the nomenclature, because the WG401 is also referred to as the "Power Drive Grip 2" whereas the WG402 is referred to as the "Power Grip WG402". In addition, compared to the WG401, the WG402 lacks both the cable-release socket and special connection for the Leaf Shutter cocking cable. I believe that the WG402 wasn't sold separately but instead, only as part of a kit.
