Modifying the transmission control strategy can offer one of the most satisfying rewards of installing a modern powertrain in an older vehicle that was previously equipped with a carburetor and an ancient 3-speed transmission. The performance gains are huge, and the benefit of increased fuel economy and drivability make your old hot rod seem new all over again. Just remember to take your time in defining what it is that you want your transmission to do and modify the shift tables as you feel fit. Remember to always leave a gap of at least a few mph from upshift vs. downshift tables and Apply vs. Release speeds to prevent hysteresis from causing unwanted shudder or other transmission misbehavior. And then just enjoy the ride! MET
Last but not least, we'll take care of our part-throttle cruise fuel economy. There's lots to be gained by turning the engine as slowly as possible while cruising as long as we don't cause the engine to lug or put it under any undue stress. The LS engines are so powerful down low that they don't even feel a 4,000 lbs vehicle at 1,100 when maintaining a steady 35-45 mph, so why rev the engine higher? The best thing to do is to program the TCM to short-shift to 4th gear as quickly as possible when you're below 30% throttle and engage the TCC quickly at lower engine speeds to lock the converter and save fuel! Don't worry, at higher throttle settings the TCM will deactivate the TCC and drop down a gear or two as we've commanded in the shift tables earlier so the overall performance will still be there when you need it, but when you don't and you're just chugging along on a cruise, do it in comfort with the engine turning as slowly as possible to save engine life, fuel and keep carbon emissions down as low as possible. You can see what we did below:
When cruising at 35-45 mph, rarely did the Corvette ever need more than 25% throttle, so below that throttle opening, we adjusted the TCC table to activate the TCC from 30 mph on up. Notice that we also had to adjust the Release values to make certain that the Apply values are always greater than the TCC Release values. Now the TCC locks up at 30 mph at throttle openings below 19% and it will stay locked even under light acceleration. This saves a good amount of fuel, lowers carbon dioxide emissions and also helps keep transmission temperatures quite low when just cruising along.