The Borg Warner Overdrive was one of the most prolific innovations for passenger cars and trucks between the 1930s and 1960s. It essentially gave what was otherwise a three speed car five forward speeds. The overdrive also provided for better gas mileage and a more comfortable ride, and as a result, they were factory installed on over 4 million cars during those decades.
But the appeal of the Borg Warner Overdrive still exists for classic cars in use today. The same reason this feature was first put into production - to allow cars to better maintain highway driving speeds - is a key reason why it is still a must-have today. You can use a vintage automobile with overdrive wherever the road takes you, whether you are running errands or heading to the next car show.
Many vintage car owners use the original Borg Warner Overdrive in their vehicles which often still work well today due to the simple, durable design and high quality parts. Others have installed a Borg Warner Overdrive during the process of upgrading their vintage driveline. Whatever the case, the overdrive is generally a low maintenance part, but knowing the basics for troubleshooting your BW Overdrive can help you keep it running properly.
Parts of the Borg Warner Overdrive
Part of what makes the Borg Warner Overdrive so easy to maintain is its simplicity. The overdrive consists of several mechanical and electrical parts. They are the:
- Planetary Gear
- Kick Down Switch
- Overdrive Lockout Cable
Of these parts, the relay and solenoid will need replacing most often as they experience the most wear. These two parts must also have the same voltage as your car, whether you have an original 6 volt car
or either a factory standard or updated 12 volt vehicle. After this, the kick down switch is the next to go bad, but the part is the same for 6 and 12 volts.
Fortunately, all three of these parts - the relay, kick down switch, and solenoid - are external parts, making them easy to fix if they do need replacement.
The other mechanical and electrical car parts will work on either 6 volts or 12 volt systems, and across vehicle models. Of the 22 vehicles that include a Borg Warner Overdrive as an option, they all used the same standard parts for easy interchangeability.
Brands of solenoids are also interchangeable. The important factor is replacing the existing solenoid with a solenoid of the same shaft length. Many cars used a one inch overdrive solenoid, but some cars like convertibles and station wagons had a solenoid with a shaft that measures an inch and a half long. A few thousand vintage Chevrolet pickups from the 1950s had a two inch long solenoid shaft.
The only main difference you need to be aware of between Borg Warner Overdrives was with the R10 and R11 models. The R10 was the most popular and uses three pinion planetary gear, while the R11 provided more durability and power with a four pinion planetary gear. The electrical components in these two different models, however, are the same.
Basic Maintenance Steps to Avoid Problems
While you have limited parts, most of which are long wearing, it is important to drive your car with overdrive in the way it was intended to avoid any unnecessary damage.
If it has been a while since you last drove a car with overdrive or this is your first time behind the wheel of one, read through our guide on the BW overdrive first so that you understand how this feature works and can use it the right way.
One of the fastest ways to damage your BW Overdrive transmission is to run it without transmission gear oil or to use the wrong gear oil. Your overdrive needs to have the correct amount of GL-1 lubrication. Do not use any gear oils higher than GL-1 and do not use modern synthetic oils. The Borg Warner overdrive consists of bronze parts, which can be corroded with the wrong oil. Synthetic oils can also be too slippery, causing the planetary gear to slide.
An overdrive will take about seven pints of gear oil and you will need to fill both transmissions when you add it.
When driving your car, avoid speed shifting with overdrive engaged. Overdrive was made to improve fuel mileage, not drag race, and speed shifting can put unnecessary wear on the internal components.
The final thing to avoid that can immediately damage the overdrive is to reverse or start in first gear while overdrive is engaged. This will instantly crush the needle bearings inside the sun gear and require a several hundred dollar repair.
Fortunately, this mistake is only possible if you bypass electrical circuits by connecting the solenoid to the overdrive toggle switch, removing the kick down switch, relay, and governor from the circuit. This is not a factory installation, but some car owners have done this over the years, and most end up later paying the repair cost as a result.
Common Technical Borg Warner Problems and Solutions
Driving your car without overstressing the overdrive and performing the basics of maintenance on the Borg Warner Overdrive is often enough to keep it running well.
Many of the problems with a Borg Warner Overdrive are due to faulty connections because wiring or tabs are corroded or have accumulated dirt. If you have any troubleshooting issues, always start by doing a thorough cleaning of the overdrive and replacing any worn wires.
But if problems continue after cleaning, here are the basic troubleshooting steps to identify and repair the issue:
- Transmission is Stuck in Overdrive
If your overdrive will not disengage, first check to make sure your shift linkages are attached tightly, then try switching the car off and on. A working overdrive will cause the solenoid and relay to audibly click. If they do click, toggle the overdrive off. If that stops the click, then the electrical problem is In the governor.
You want to remove the cover of the governor and ground it by touching the cover to the transmission case. If you hear a click at that point, there is a short circuit in the governor that will need to be repaired. If there is still no click in the relay and solenoid when you turn the ignition on, the electrical problem lies in the solenoid.
- Overdrive Does Not Kick Down
If overdrive does not kick down when you press the throttle to the floor, you most likely have a problem with the kick down switch. The first test for this is to connect a jumper from the ignition terminal on the kick down switch to ground. If this does not kill the engine, the issue is likely a badly adjusted kick down switch. Readjust and try again.
Your next check is whether or not the engine dies when you depress the kick down switch at normal speed. If it does, disconnect the wire at terminal #6 on the solenoid and try once more. If the engine dies this time, the switch is the problem. Otherwise, the wire likely has a short.
If the engine did not die when you first depressed the kick down switch, check the insulator in terminal #6.
- Fuse Fails Consistently
Overdrives use one fuse on the relay. If your fuse is having issues, first check that the wire still connects the relay and the solenoid. You should also check the voltage on the solenoid at the #4 terminal. If the voltage there is less than 5.5 but you have a charged battery, replace the wire with a new 10 gauge wire.
- Overdrive Will Not Engage
This is one of the most common problems with an original overdrive and has the most potential solutions depending on what causes the issue. Most often, the reason is electrical. To confirm, test drive your vehicle with the overdrive toggle on or cable pushed in. If there is no automatic shift to overdrive above 28 miles per hour, it is an electrical issue.
Start by checking for power at each side of the fuse on the relay. You may need to clean any corrosion off of the mounting clips on either side. If there is no power, look for the break in the wire and replace it.
Next, check the wire on the governor underneath the car for any fraying. Remove the cover on the governor to connection points inside as well to make sure everything is moving and not coated in oil.
If the problem persists, connect the governor wire to ground with the ignition on. If you do not hear a click from the relay, there is an open circuit. Trace the battery voltage from the battery wire to the kick down switch and then to the relay. If there was a click in the relay but no click on the solenoid, this means the issue is with a solenoid which will either need to be repaired or replaced.
There are a range of additional issues that can occur with an overdrive and other troubleshooting steps may be needed. But the good news is that the overdrive is durable and relatively simple to take apart and put back together, even if you are new to vintage cars.
Disassembling, cleaning, and playing around with the different parts can often lead you to the issue with your overdrive. It can also be helpful to have the Borg Warner Overdrive Service Manual and many additional free resources here on our website to help you understand the various parts and workings of the overdrive.
When you need any additional parts in the process of maintaining a Borg Warner Overdrive, Vintage Auto Garage has an extensive inventory of high quality vintage car parts to restore classic car overdrives to full functionality. Our overdrive parts include solenoids in multiple shaft lengths, overdrive kick down switches, wiring overdrive relays, and replica pull cables.
Our team can help you identify which parts are the right fit for your car model and overdrive to help make sure your repair process goes as smoothly as possible. Search through our vintage Borg Warner Overdrive parts or contact us for personalized assistance with your purchase.