Rancho Bronco Overdrive (b-100)

Rancho Jeep Supply (Later to be known as Rancho Suspension) developed an aluminum alloy adapter for use with a Borg-Warner overdrive that would mate up with the Bronco's Dana 20 transfer-case. Model B-100. The picture to the right shows the output housing that is removed from the transfer-case and the overdrive unit that is put in its place. As evident in the picture the rear drive must be shortened 9" to use the overdrive.

An electric control automatically engages and disengages the overdrive while the vehicle is moving. The engagement of the overdrive is controlled by a dash mounted handle that is connected to the overdrive. This can be done at any speed. When engaged (Handle-In) the vehicle automatically shifts into overdrive at approximately 30 mph. It disengages when the speed drops below 30 mph. To disengage the overdrive the Bronco should be standing still. A kick-down switch is also used by the overdrive. By simply flooring the accelerator pedal the overdrive is disengaged returning the Bronco to its original gearing.

An article covering the "New Overdrive" appeared in the October 1968 Four Wheeler magazine, pg. 22-25. (Thanks to Todd Z. for supplying the article) The article gave credit to Clarence Shook and Basil "Smitty" Smith as the team that created the Bronco overdrive. Ken Roggy Ford of La Puente California was originally selected as the "Exclusive" distributorship of the B-100. The article went on to mention that since the Bronco has power to spare (V8) that the overdrive would make full use of the power giving increased fuel economy and performance. The following is the results of their testing:

MPH  OVERDRIVE (RPM) W/O OVERDRIVE (RPM)  
35      1200           3100
65      2600           3900      
70      2900           LOUD

Gas mileage increased 27 percent (17.5 vs 13.7)

The article finished up by saying that the overdrive was a "Bronco Saver".

Here's a couple of pictures from the Bronco Overdrive Installation and Operating Instructions manual that might prove useful to those who have one.

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