The Borg Warner Overdrive

By Tom Endy, Westminstel; Calilornia

The one on the left, with the words on and off, is the power switch. The one on the right is the spring loaded over-ride switch. Pushing it down against the spring completes the circuit and over-rides the governor.

For the Model A Ford: production, an after market ring and pin­ The overdrive has two controls, one is a Over the last 30 years the addition of an ion gear with a higher gear ratio of 3.54: I "T" handle the driver pushes in to initiate overdrive to a Model A Ford drive train became available. This new ratio is higher the overdrive action. The secone! is an has become a popular and practical conve­ than the standard Model A ring and pinion electrically operated solenoid that the nience. The very first to bc used in the ratio of 3.78: I. The higher ratio allows the drivcr did not directly control and was 1970's were the Borg Warner conversions. Model A to clip along at a little highe r usually not aware it existed. The scenario Cottage industries were developed to speed, but with the engine still turning usually went like this: the driver would be modify the Model A torque tubc and drive over at the nominal 2,000 rpm. The draw­ out on the highway and would desire to shaft to utilize Borg Warner overdrives back is that you will find yourself shifting use the overdrive. He would push in the salvaged from the 1950's and 1960's Ford, into second gear more often when encoun­ "T" handle. The overdri ve planetary sys­ Nash, Studebaker, and other cars. Today, tering hills. This trade off has to be con­ tem would put the car into what is known there are companies such as the Mitchell sidered when contemplating installation of as a Hfree wheeling" mode (more on that Co. that produce a factory-built overdrive the higher gear ratio. An overdrive, on the latcr). The car will not actually go into for the Model A Ford. While the trend is other hand , provides the capability of overdrive until it rcaches a speed of about toward the factory-built overdri ves, there shifting back and forth from a low ratio to 35 mph. At that point the governor, which are still many of the Borg Warner conver­ a high ratio. The thing to keep in mind is a component of the overdrive, will close sions around. Though somewhat misun­ about an overdrive is that it does not a switch that will electrically power the derstood, they can still be a practical low increase the top speed capability of the solenoid and the car will go into overdrive. cost addition to a Model A Ford. car. Whatever top speed your Model A is Borg Warner overdrives have an over­ capable of achieving, the installation of an speed ratio of 33.3%. When in overdrive Why An Overdrive: ovcrdrive will not change that. What the the car will travel 33.3'Yo faster for the When Model A Ford production began the overdrive allows you to do is clip along at same engine rpm. Should the driver want nation' s roads and highways were a far cry a nominal 60 mph with the engine turning to pass a car ahead and desires to tem­ from what they are today. A speed of 45 over at the desired nominal 2,000 rpm. porarily drop out of overdrive, a "kick­ mph was considered to be clipping along. This higher speed is obtaincd without down" switch was providcd righ~ bel'ow The Model A was designed to run at a strain to the cngine, the ridc is very the gas pedeil. The driver momentarily nominal 45 mph with the engine turning smooth, and gas mileage docs not suffer at pushcd the gas pedal to the floor to actuate over at a nominal 2,000 rpm. You could the higher road specd. the switch. The switch will open the run all day long at this speed without hurt­ solenoid circuit and drop the car out of ing the engine. You could also accelerate How They Orig1inally Worked: overdrive. The car will remain out of over­ up to 65 mph, or even faster, if the car was The original "modern car" Borg Warner drive while the driver accelerates around capable of it. However, anything above the installations werc almost an intcgral part the car he is passing. Whcn the drivcr nominal 45 mph for any length of time of the standard three speed transmission. eascs up on the gas pedal the solenoid is was tough on the car. You would not want The overdrive had an open housing at the reactivated and the car goes back into to sustain these speeds all day long. Not front end that bolted up to the rear of the overdrive. The solenoid circuit was con­ only would the engine not last long, the transmission that had an open housing at trolled by an electrical relay. The kick shaking and vibration of the whole car the rcar. The transmission and the over­ down switch had an additional feature. A does not make for a smooth, pleasant ride drive shared the same oil volume. The second set of contacts momcntarily short­ for the occupants. As the nation's roads overdrive unit has a planetary gcar system ed out the ignition circuit. This caused the improved after the Model A went out of that provides a two speed gear change. engine to quit firing for several revolutions

4D The Restorer· March/April 2005 ... to allow the engine to spool down enough ing is then bolted into place between the ago to Bill Swigart of Redding, California to release the overdrive gears. two flanges. The overall length of the (530-221-1628). Although the market for modified torque tube with the installed Borg Warner conversions has diminished, Reverse Gear: Borg Warner overdrive unit has to be Bill, however, is still in the business and A Borg Warner overdrive will not operate exactly the same length as is the original does support the existing Bert Hiller over­ in reverse gear because it has an over run Model A torque tube. Any variation of the drives in service and will build and sell a clutch incorporated in the output shaft length and you will not be able to slide the Borg Warner overdrive if ordered. One of when it is shifted into overdrive. The free bolt into place that attaches the two rear the advantages of the Bert Hiller\ Bil,1 wheeling rollers in the over run clutch radius rods to the front of the torque tube. Swigm1 overdrive is that they are sold as a allow operation in only one direction ­ This is a very critical dimension. Another complete kit. This includes the "T" handle forward. When the standard modern car critical dimension is the alignment of the cable, a 6 or 12 volt solenoid, a governor, three speed transmission is shifted into two flangcs. They must be perfectly per­ a power relay, the speedometer cable reversc a horizontal shaft inside the trans­ pendicular to the torque tube. If thcy are extension, and the wiring and installation mission is pushed toward the rear engag­ even slightly cocked it will throw off the instructions. Borg Warner overdrives were ing a mechanism inside the overdrive that alignment of Ihe two drive shaft sections meant to utilize the governor. However, pushes it out of overdrivc. When a Borg inside the torque tube. The stock Model A very few Model A hobbyist take advan­ Warner is converted for use in a Model A drive shaft also has to be modified by cut­ tage of the excellent feature the governor Ford it is mounted in the middle of the ting away a center section to accommodate offers. torque tube. It has no mechanical relation­ the overdrive unit. A spline has to bc cut ship to the Model A transmiss ion. The into the rear of the front section and anoth­ Typical Model A Use: overdrive is not automatically pushed out er into the front of the rear section. The Most people who have a Borg Warner of ovcrdrive when the Model A driver two splines make the attachment to the installed in their Model A have a very sim­ shifts into reverse in an attempt to back overdrive unit. The rear shaft section is ple hookup. A small panel is attached to up. Thc Model A driver must manualIy rcferred to as the stub shaft. One end is the side of the steering column with a muf­ take it out of overdrive by pulling the 'T' splined into the overdrive and the other fler clamp. The panel accommodates the handlc out and deactivating the solenoid. end is fitted into the p,inion gear of the dif­ "T" handle and a simple on\off switch. An If a Model A driver attempts to back up terential. If there is any misalignment of optional indicator light is sometimes with both the "T" handle in and tl,le the torquc tube flangcs it will cause a side included. Electrical power is applied solenoid powered, damage will occur to loading to the stub s haft and thc front through the switch to the solenoid. The the overdrive gears. If a Model A driver shaft. The side loading will increase the optional indicator light lets you know attempts to back up with the "T" handle wear on the spTines and eventually cause when power is being appl,ied. The Model in , but the solenoid not powered, no dam­ them to tcar up. Side loading can also put A driver simply pushes in the "T" handle age wiE occur, but the car wi II not back a strain on the tapered end of the stub shaft and flips the switch when he wants to use up. As the clutch is cngaged the car will where the pinion gear is mounted. This the overdrive. It is prudent to only use the just sit there and go nowhere. This is one can cause the shaft to break right at the overdrive when in high gear above 45 of the major drawbacks of the Borg pinion gear key. The flanges that Bert mph, or in second gear when climbing a Warner overdrive when converted for use Hiller L1sed were more than an inch thick hill, otherwise, it will causc the engine to in a Model A Ford. to gi ve superior strength to the entire drive "lug." train. Bert also used a jig to provide proper The Model A Conversion: alignment while welding cvcrything into It is also prudent to take the car out of In past years there wcre a number of peo­ place. overdrive by turning power off to the ple with cottage industries offering the solenoid and pulling out the "T" handle converted Model A Borg Warner over­ Another consideration is the oil seal when coming down a I'l ili. The frec wheel­ drive. Some were excellent, some were design. The oil inside the overdrive must iug phenomenon explained earlier will marginally acceptable, some were not so be prevented from leaking out both the allow the car to increase in speed as ,there great. Probably the best were those built front and the rear. If oil should get past the is no engine braking when in the free by Bel1 Hiller of Vancouver, Washington. front seal it will drip out on your garage wheeling mode. There are several distinct Bcrt built several thousand of them. His floor right under the U-joint. If the oil gets disadvantages to this simple hookup. product was excellent because he under­ past the rear seal, the only indication you stood the nced for propcr alignment. I will have is that the differential is manu­ Damage To The Overdrive: spent part of a day at Bert's shop a number facturing oil, caused by oi l leaking past the If the Model A is parked with the "T" han­ of years ago and he cxplained 10 me why seal, down the rear section of the torque dlc pushed in while the solenoid is still alignment was so critical. In order to pro­ tube, and into the banjo. fai lure of thc rear powered and the drivcr forgcts and leaves duce the Model A conversion a center sec­ seal can cause oil starvation and failure of the switch on and latcr attempts to back tion of the Model A torque tube and drive the overdrive, which will be masked by up, damage will occur to the overdrive shaft must be cut away. The torque tube the fact the oil is accumulating in the gears. If only the "T" handle was left must have mounting flanges welded to the banjo. pushed in, no damage will occur, YOLl two sections, one to the rear of the front merely won't be able to back up until the section, the other to the front of the rcar Bill Swigart: "T" handle is pulled out. section. The Borg Warner overdrive hous­ Bert Hiller sold his business several years

Marc h/Apr il 2005 • The Restorer ~ A Dead Battery: applied to one side of the solenoid control solenoid power switch is in the off posi­ If the Model A is parked while the relay. The fly-ball is set for a speed of tion. When I am about to enter a solenoid is still powered, and left that way about 35 mph. The Model A would be bet­ (Southern California) freeway I push the overnight, the battery will be dead by ter served if the governor speed was 45 "T" handle in and put the powcr switch to morning. If you were to look inside a mph. However, I know of no way of the on position. The car is not in overdrive solenoid you will see two sets of contacts, adjusting the governor for a differcnt at this time. As I accelerate down the on one large, one small. When the solenoid is speed. The overdrive circuit is hooked up ramp and excecd 35 mph I will notice that initially powered, it needs about 30 amps such that thc power relay does not close the indicator light has come on. This tclls (on a six volt system) to mechanically until it sccs the ground from the governor me I have passed 35 mph, the governor actuate the solenoid. The large contacts switch. This mcans that even though you switch has closed , and the solenoid is provide this power to a separate coil. As have placed the power switch to the on powered. As I continue accelerating, the the solenoid actuates, the small contacts position, there is no power to thc solenoid car won't actually go into overdrive until I close powering another scparate holding until the relay closes. The advantage of momentarily easc up on the gas pedal to coil and the large contacts open dropping this is that you canl10t go into overdrive allow the overdrivc gears to engage. Once out the first coil. The purpose of this until the car is abovc 35 mph and if the car I do that, the car is in ovcrdrive. I can arrangement is that once the solenoid is is parkcd with the on\off switch in the on continue down the freeway at speeds of 60 actuated it does not need 30 amps to hold position thc solcnoid is not powered. This to 65 mph. If traffic begins ,[0 slow and I it in, only a few amps for the holding coil eliminates the possibi:lity of backing up am forccd to slow down below 35 mph, are required. Those few amps, however, and damaging the overdrive gcars, and the governor switch will open, the are enough to drain your battcry prevents the possibility of running the bat­ solenoid will drop out, the indicator light overnight. Because of the initial 30 amps tery down if left on overnight. The other will go out, and the car will bc out of required to actuate the solenoid, it is a advantage in using thc governor, is that the ovcrdrivc. When traffic resumes and I am good idea to put the solenoid on its own overdrivc acts like an automatic transmis­ able to travel above 35 mph , the car will fuse circuit separate from the car's electri­ sion. The drivcr docs not have to continu­ automatically go back into overdrive as cal fuse circuit. ally switch thc overdrive in and out. The before. All of this willi continue to happen governor will do that automatically. W,i th without having to touch any of the con­ Use Of The Governor: the power switch turned on and the "T" trols. When I am off the freeway and I Just about every Model A Borg Warner handlc pushcd in, the car will go into over­ encountcr a hill that is too steep to climb overdrive in service has the governor drive automatically when it reachcs 35 in high gear, but not steep enough for sec­ installed, but few are hooked up to any­ mph , wiJl automatically drop out whcn ond gear, I can push in thc "T" handlc, thing. Were the governor not instal 'led, below 35 mph and go back in whcn it close the power switch and actuate the there would be a large hole in the top of again goes above 35 mph. spring load cd ovcrride switch and the car the overdrive that would emit large quanti­ will go into second gcar overdrive. The car ties of oil unless the hole is somehow Second Gear Hill Climb: will stay in overdrivc cvcn if I release the plugged otf. Over the years I have owned The governor hookup described abovc will ovcrride switch as long as I kccp the gas three Model A's that I installed a Bert prevent you from using the overdrivc to pedal down and not allow the ovcrdrive Hiller overdrive in. I still have one of climb a hill in second gear becausc, more gears to disengage. them, a 1929 Coupe. All three ulil ,ized the than likely, you will be below thc govcr­ governor and were controlled by a power nor speed of 35 mph. However, there is a Kick-down Switch: relay. There are a number of advantages way around it. An override switch can be A kick-down switch could also be incor­ to utilizing the governor. added to the control panel attached to the poratcd in the iVlodel A conversion. steering column. This switch should be a However, this is not realiy necessary since The Governor Hook Up: spring loaded type of switch. When the the Model A driver has access to the There are several ways that a governor cir­ switch is activated and held in the on posi­ on\off switch, which servcs the same pur­ cuit can be connected. One such hookup is tion it will put the car in overdrive cven pose as a kick-down switch, as it will shown in schematic form at the enc! of this when it is under the 35 mph governor remove power from the solcnoid. The article. The governor is located on the top spced. How it works is the switch, when "modern car" drivcr did not have this of the overdrive and is a circular looking activated, provides a ground to the rclay option and for that reason a kick-down device screwed into the overdrive housing. the same a$ the governor would do. The switch was necessary. The idea of shorting It has one single electrical connection spring load prevents the switch from being out the Model A ignition, even momentar­ point. Inside the governor there is a set of inadvertently left in the on position. ily, may not be prudent, as a Model A will open contacts that are controlled by a fly­ have a tendency to backfirc. ball govcrnor that is drivcn by a small gcar The Driving Scenario: in mesh with a worm gcar on the overdrive The Borg Warner in my 1929 Co upe is The Power Relay: output shaft. The fly-ball rotates and at a hooked up as described above, including It is desirable to use a powcr relay to con­ given speed will close the contacts. One of the spring loaded override switch. The trol power to the solcnoid. The on\off the contacts is grounded to the case, so driving scenario usually goes like this: switch apphes battery powcr to one side of when the contacts are closed it is provid­ while driving around town on surface the relay coil. The governor or the over­ ing a ground at the single electrical con­ roads there is no need for use of the over­ ride switch apply a ground to thc other end nection on the governor. This ground IS drive. Thc "T" handle is pulled out and the of thc coil to cause the relay to actuate.

~ The Restorer· Ma rc h/April 2005 The contacts of the relay actually provide The Model A Flywheel: Model A Do's, Don'ts and Can'ts: the power to the solenoid. A 6 or 12 volt When a Model A is equipped with a Borg The application of the Borg Warner over­ automobile headlight relay will work very Warner overdrive it is a good idca to have drive in a " modern car" was designed to well as a power relay for the overdrive cir­ about 10 lbs of weight removed from the be fool proof so the dri ve r could conve­ cuit. Twelve volt headligh t relays are still flywheel. A Borg Warner overdrive does niently operate the overdrive and not do available at most auto parts stores. The six not immediately drop into overdrive when damage to it. Protection was provided volt version is probably not available in the solenoid is actuated. The driver has to through a combination of use of a gover­ stores, but can usually be found at swap momentarily ease off the gas pedal and nor and the reverse defeat shaft in the meets. It is best to use a headlight relay allow the engine to "spool down" slightly manual transmission. The installation of a and not a hom relay. Headlight relays are to allow the overdrive gears to engage. Borg Warner in a Model A Ford creates more robust and were designed for sus­ With the flywheel slightly lightened the so me do's and don'ts that the Model A tained use. A horn relay was designed for engine wi[i] spool down a little quicker and driver should be aware of. short bursts and will overheat ifapplied to the time required to drop into overdrive is sustained use. The headlight relay can eas­ shortened. ily be installed in the U-shaped frame cross member located just in front of the service brake cross shaft. There are unused holes in the cross member that a bracket can be attached to. The relay is then mounted to the bracket and is nicely tucked away out of sight in the "U" of the cross member.

Solenoid

Phot() courtesy ofUs Andrews

Pertinent Facts: Fact #1: While traveling down the highway, you can push the T-handle in without pushing in the clutch (solenoid not powered).

Fact #2: While traveling down the highway, you can pull the T-handle out without pushing in the clutch (solenoid not powered).

Fact #3: While traveling down the highway, you can push the T-handle in without pushing in the clutch while the solenoid is powered.

Fact #4: While traveling down the highway, you cannot pull out the T-handle while the solenoid is powered. Clutch in or not, the sys­ tem just won't allow the handle to come out until the solenoid is de-powered.

Fact #5: While sitting still with the T-handle pushed in (solenoid not powered), you cannot back up in reverse . No damage to the overdrive will occur if you attempt it, the car simply will not move when you let the clutCh out.

Fact #6: While sitting still with the T-handle pushed in and the solenoid powered, you should not attempt to back up in reverse as you will do damage to the overdrive.

Fact #7: When parking the car with the solenoid still powered, you will have a dead battery if you leave it that way long enough.

Fact #8: While traveling down the highway with the solenoid powered, but with the T-handle pulled out, the car will operate as normal as if there were no overdrive installed.

Fact #9: While traveling down the highway with the T-handle pushed in and the solenoid not powered, you will be in straight drive (not in overdrive), but the car will be in a "free wheeling" mode, in that the rear wheels can travel faster than the engine is driving them (as in going down a hill).

Fact #10: While traveling down the highway with the T-handle pushed in and the solenoid powered, you will be in overdrive.

Fact #11 : While traveling down the highway with the T-handle pulled out and the solenoid not powered, you will be in straight drive as if there were no overdrive installed.

March/Ap ril 2005 • The Restorer ~ Borg - Warner Overdrive Circuit

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The Restorer· March/April 2005