The major change was the planetary gear set in the OD section. Chrysler changed the angle of the gear set. The early ones for both the A500 and A518 had breakage problems and the factory upgraded the gear set and problems seemed to go away. They upgraded the A518 first and then later the A500. The replacement set is the same for transmissions. Core prices are all over the place from what I've seen, so I guess it boils down to what you feel comfortable with. If you follow the A500/A518 on electrical connectors thread recently posted, there is some additional information you might want to read.