[Alan Roehrich]

Greg, with the 700R4, it was a matter of a lack of clutch pack and band capacity, as well as a weak over run sprag. You do not see a lot of planetary failures with the 700 R4, or at least I have not seen more than a very few in the 20+ years I've worked on them. The over run sprag failed regularly, as well as the sun gear shell.

The problem with a single compound planetary would be size, weight, and complexity. I don't think there'd be enough of a reduction in rotating mass/weight by replacing two planetary sets with one larger more complex compound set. If there was a lot to be gained, the OEM's would already be doing it a lot, just for the fuel economy and emissions gains, as even a minuscule gain for them is big, spread over their unit production run.