With Reverse and 5th Gear so close to each other on the T56 / T56 Magnum Six-Speed manual transmissions, the potential for accidentally engaging reverse whilst changing for fifth is a serious and potentially dangerous risk which can be mitigated by utilising the Reverse Lockout Solenoid. I have been unable to get a definitive view on the merits of how this is resolved other than it’s important to use a safety lock out to avoid selecting reverse whilst moving !
There are a number of manual workarounds and fudges discussed across the web all of which seem to leverage the brake light wire so the solenoid is “aware” that the driver is applying pressure upon the brakes and energises to disable the transmission gate. The problem with this, is that it is potentially hazardous given the risk of accidentally engaging whilst slowing or undertaking a gear shift and putting your car into reverse resulting in potentially catastrophic damage.
Numerous vendors offer a solution to this, I elected to acquire a unit from American Powertrain purchased via Summit Racing to eliminate this problem. The outputs from the transmission solenoid connect to the unit which enables reverse to be safely selected, only when you are stationary.