Another option would be a trans that was used pretty frequently ahead of a 3.08 rear axle, the TH 350C. It has a locking clutch in the torque converter that gives approximately a 10% RPM reduction at light throttle cruise by eliminating the built-in slippage in the converter. That one uses a 3-switch series of controls, a vacuum switch that senses engine load, a brake switch that disengages converter lockup anytime the brake is used, and a governor pressure switch in the valve body that sets the minimum lockup speed. All three switches must be closed to send power to the solenoid valve that locks in the converter clutch, but no computer is needed for the system to function.

BTW, converter locking clutches are nothing new- - - -the 1949 Studebaker automatic had one, and also the 55-57 Packard Ultramatic. No electrical controls were used on either one of them, however.
Jerry


"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
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