Borg Warner R10 R11 Overdrive Free Report

Thank you for requesting our Borg Warner Overdrive report. This report is meant to assist owners with the operation and maintenance of the Borg Warner R-10 and R-11 Overdrive transmissions.

Some history: The original Borg-Warner Corporation was formed in 1928 by the merger of Warner Gear which itself was founded by Thomas Warner in 1901 and Borg & Beck founded by Charles Borg and Marshall Beck in 1903. The company was best known as the supplier of Borg Warner Overdrive units from 1930's to the 1970's and as the developer of the Studebaker three-speed automatic transmission introduced in 1950. Ford took up development of the transmission in Studebaker's place in 1955. The early Ford automatics are derivatives from the early days of Borg Warner. And the world famous Borg Warner Indy 500 trophy has been provided to the annual winner of the Indy 500 by the company since 1936.

As the roads improved and car speeds continued to increase there was a need for a transmission that would allow the engine to turn slower at higher speeds and still have the low end torque for climbing hills. To address these needs, the Borg-Warner overdrive transmission was first introduced in the 1934 Chryslers and DeSoto then used by Ford, GM, Hudson, Kaiser-Frazier, Packard, Studebaker and Willys, all total of 13 auto manufactures used this overdrive transmission. In total, there were 1 million OD transmissions produced.

Ford first installed the Borg-Warner overdrive's in the Lincoln Zephyr in 1941. Then became optional on Ford and Mercury cars from 1949 and then faded from use in cars in the '60s. Ford pickups continued to offer overdrive into the '70s.

The overdrive transmission are electro- mechanical devices and require several electrical and mechanical components to operate: Solenoid, Governor, Kick Down Switch, Manual Push Pull Cable, Relay and wired together using a wiring harness.

The R-10 has a three pinion planetary gear set and adequate for street applications, the R-11 utilize four pinion planetary gear set and overall a stronger transmission and was mostly found on heavier trucks.

Operating the overdrive is simple. There is a manual control cable mounted under the dash and used by the driver to manually engage or disengage the transmission. Pulling the handle out takes the transmission out of overdrive and then operates like a conventional three speed. Pushing the handle in allows the engagement of the overdrive and then the operation is essentially automatic.

Driving a car with overdrive requires the driver to understand the operation and may require some adjustment in driving style. With the overdrive engaged (handle in), the transmission will freewheel below 20-30 mph depending on the car's rear end gearing, which means the engine will drive the wheels, when lifting off the throttle the wheels won't spin the engine and the car will coast as there is no engine braking. However, once the car is up to the required speed will say 28 MPH the governor closes the electrical circuit, then when the driver momentarily releases the throttle the solenoid is activated via a relay and locks the sun gear in the planetary set and the transmission shifts into overdrive which also means there will be compression braking when lifting off the gas. Remember this happens when speed is above governor speed (28 MPH).

Shifting out of overdrive happens in two ways. Slowing down under the governor cut-off speed (28 MPH) causes the solenoid to release. Or, if the throttle is floored the kick-down switch is depressed. This does two things, it interrupts power to the OD solenoid and also grounds the ignition coil momentarily, this grounding stops the engine for a brief moment and takes the torque off the transmission similar to depressing the clutch and allows the solenoid shaft to retract and disengage. Internally the solenoid shaft is trapped and can not be released, by shutting off the ignition system briefly releases the load on the transmission and the solenoid shaft and allows the solenoid to release the sun gear (which means the transmission is in direct drive) and the ignition system is back on. All this happens very fast. The flyweight governor located on the tail shaft activates around 28 MPH, this means the overdrive can not be activated below this speed.

Around town in traffic using overdrive say in second gear is like having an automatic, as the transmission will shift back and forth between direct and overdrive as the speed varies above and below governor speed.

On the highway and cruising in third gear the transmission is in overdrive mode. When you want to pass another car or jump on the freeway the driver simply depresses the gas pedal and this will activate the kick down switch and causes a downshift taking the overdrive out for passing. Then once letting off the gas the overdrive will be back engaged.

When parking and leaving the vehicle in overdrive there is danger the car can roll away. Best practice is to pull out the OD handle, this ensures that the OD is not engaged and not free wheeling, then put the shift lever in 1st or 2nd gear and set the park break. This will ensure that the compression of the engine is acting on the rear wheels and in a manner to stop the car from rolling.

Never reverse the vehicle with OD engage, if all the electrical and mechanical devices are connected as designed originally this will never happen. However over the years car owners have removed manufacture safety features and installed switches on the dash to activate the solenoid along with maybe an indicator light. This will work until someone else drives the car and does not realize what the dash light means, then puts the car in reverse with OD engages and CRUNCH!! Goes the gears and bearings and a very expensive repair. therefore It is never recommended to bypass the electrical circuits that were designed to prevent this from happening.

Now that we covered overdrive basics, we will dig further into some specifics around the OD electrical system. We mentioned earlier that 13 car manufactures installed the Borg Warner R10-R11 transmissions and essentially all electrical operation is the same. However, all companies used different colored wires making it difficult to troubleshoot and change parts. For this reason we have developed a simple to follow wiring diagram.