Originally Posted by
Buzz
The 700R4 shifts are 100% mechanical (not controlled by any PCM / ECM). The TCC lockup is a simple 12 volt supply (no PWM etc.). It can be as simple or as complicated as you wish.
The most simple means is a 12 volt ignition circuit, routed through a brake switch that interrupts the voltage, connected to a normal open pressure switch on the 4th gear circuit of the valve body (most / all 700R4 came with this switch in place). With this method the TCC is locked in 4th gear at all times - except when the brakes are applied.
The next most complicated method adds a vacuum switch, which interrupts the the voltage when the vacuum drops (under load).
The most complicated method adds a speed component - which in a TPI / TBI vehicle was controlled by the OBD1 ECM. If memory serves B&M used to offer such a kit.
As long as the vehicle is not dreadfully underpowered the most simple method works just fine.
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