Upgrading a Borg-Warner Overdrive to 12 volt

Borg-Warner designed electric overdrive transmissions were introduced in 1939 and used in 11 different car models from 1939 through the 1960's. Chevrolet Ford Chrysler Hudson Packard and Studebaker were among the car manufacturers that all used the same Borg-Warner designed overdrive. The mechanical portion of the overdrive transmissions is all based on the same operating principle and most of the internal parts specific to the overdrive are interchangeable between models.


The electrical parts of the overdrive transmissions were also based on the same working theory, and most share the same basic wiring diagrams. In addition, all of the Borg-Warner overdrives had a governor, relay, kickdown switch, and solenoid. Most of the electrical parts are interchangeable among models.


The important thing to remember when upgrading from 6-volts to 12-volts is…the relay kickdown switch, and governor will all work fine on 12-volts. The one thing that have to be changed is the 6-volt solenoid, which must be replaced with a 12-volt solenoid.


You Cannot Just Install a Voltage Reducer Because…
There are two different sets of contact points inside of an overdrive solenoid, along with two different sizes of wire windings. T he heavy windings are what "pull" the overdrive in gear. Once the overdrive is engaged, the " holding coils " take over and hold the overdrive engaged. One single voltage reducer cannot control two different amperage loads.


What if I just run the 6-volt Solenoid on 12-volts?
All will be fine for about an hour until the holding coils and contact points overheat and burn out. Then you have just ruined your expensive, and hard to find overdrive solenoid.


What Will Interchange?
Most all of the 6-volt overdrive solenoids can be replaced with a 12-volt solenoid of the same type. For example, a 1950 Ford 6-Volt Solenoid can be replaced with a solenoid from a 1956 and newer 12-volt overdrive transmission.


Be sure to compare the shaft lengths of your original 6-volt solenoid with the replacement 12-volt solenoid. Most all 6-volt and 12-volt solenoids used the same shaft length. A few known exceptions include Lincolns, and Packard’s of the late 40's and early 50's, along with some Chevrolet truck applications from the late 50's and early 60's. Also most all convertibles and station wagons used the longer shaft solenoids because of the extra cross member in the frame.

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