Maybe this thread is the place to ask this question. Now that I am locked in for a while to a mild 350 with a street torque cam and a 2.79 rear gear, I am wondering whether to trade/sell my rebuilt TH350 transmission for an R700. People and articles tell me that the TH350 is more reliable than the R700, but of course the limit to only three speeds and the fact that I have the early non-lockup TH350 leads to lower mileage for two reasons. Assuming I keep the 2.79 rear gear, what about the change to optional planetary gears on the TH350? The low gear will only change from 2.52 to 2.70 and the gears are expensive so is it worth the change? The good part of that idea is that high gear remains 1.00 so the 2.79 ratio is still available for cruising mileage.
My rough calculations indicate that If I keep the 2.79 rear gear and add the lower ratio planetary gear, the new low gear will be what it would be if I had a 3.00 rear gear, not a great improvement, but still some better performance while retaining the high gear mileage. Any comments from someone who has tried the lower ratio planetary gears in a TH350?

Don Shillady
Retired Scientist/teen rodder