The Ford "Skyway" Columbia Overdrive

Before the Borg Warner R-10 and R-11 electric overdrives became popular in the 1940's there was the Columbia overdrive rear end overdrive option. It could be installed by the local Ford dealer and offered a higher top speed and more important a lower engine rpm at normal highway speeds. The ratio of the Columbia overdrive was 28% very close to the 33% of the later Borg Warner electric overdrive. Unless you grew up in the era, you likely do not know much about a Columbia overdrive or how it operated. So stay tuned as you get a crash course in Columbia 101.

The Columbia overdrive rear end was an early design overdrive that was adapted to the stock Ford rear end housing, and was designed to provide a dual ratio for the rear end. The Columbia rear end was an option from Ford beginning in 1934 (could be retro fitted to a 1933) and prior to the Borg Warner overdrive transmissions which would become a Ford option beginning in 1949. It was the Borg Warner overdrive transmission that would later contribute to the demise of the Columbia dual-ratio rear end. Lets learn more.

Originally developed by the Columbia Axle Company in Cleveland, Ohio, the two-speed axle was first used as an option on the 1932 Auburn. Ford first offered it as a conversion for their 1934 models; it was later offered as a factory-option on the 1937-'41 V-12-powered Lincoln Zephyrs, Continentals and Custom models, and 1939-'41 Mercury's and Fords with the Flathead V-8.

The axle was supplied as a kit to be installed by Ford dealers or by independent authorized garages. Only a few of the 1933-1934 kits were sold, and they are considered very rare today. The axle was redesigned and improved for the 1935 Ford model year, and by mid-year, was called the Columbia “Two-Speed Axle” even though the differential carrier casting (A-6) was still marked “Dual Ratio Axle”. The axle was also an option for the new 1936 Lincoln Zephyr and later, the new 1939 Mercury. Ford, Mercury and Lincoln Zephyr cars could be ordered with a Columbia but it was installed by a Ford authorized independent shop before delivery. 

When the Columbia rear end unit was fitted to the original banjo-style Ford rear-end, the driver's side axle and the left axle housing were retained, but the passenger-side axle and housing had to be replaced. The new right side axle was shorter to make room for the planetary and sliding clutch assembly. The new right axle housing incorporated the mounting bracket for the vacuum canister and an opening for a shifting lever that was attached to the end of the canister's vacuum piston. 

The piston rod had a clevis assembly that attached to the sliding clutch. When the axle is in low gear, the sliding clutch is engaged, locking several planetary pinion gears and a center sun gear into a sort of "reverse flywheel" cut into the inner diameter of the ring gear. The outer ring gear then turns the axles. When the overdrive is engaged, the vacuum canister retracts the sliding gear and stops the sun gear from spinning. This allows the differential ring and pinion to spin freely and causes the stationary clutch to engage, allowing the ring gear to rotate the internal pinion gears. The sun gear, however, stops rotating when the sliding clutch is disengaged. The rotation of the ring gear turns the pinion gears about the sun gear, which allows the "reverse flywheel" and the axle shafts to rotate in the second speed.

Starting in 1937, the marking on the differential carrier casting was changed to “Two- Speed Axle” or “Overdrive Axle”. ’46-’48 castings were marked “Overdrive Axle”. 

In 1940, Mr. E.L. Cord sold the Columbia Axle Co. to a Cincinnati investment group represented by Messrs. W.E. Schott (who already controlled a sizable number of auto-related businesses) and Lewis Goldsmith. These two men became the new President and Vice-President, respectively, of the Company. Production and distribution of the two-speed axle continued as before, however, they were not available from 1942-1945, due to WW II. Production was resumed in late 1946 with Ford and Mercury dealers obtaining the axles from the Truckstell Company, with distributors located at key points from coast to coast. The Columbia Overdrive was now called “Skyway Drive” and had a new electric control, to activate solenoid, instead of manually as it was prior. 

The 1949 introduction of the new all electric shift Borg-Warner overdrive transmission option by Ford, made the Columbia overdrive obsolete, which spelled the doom of the Columbia Axle Co. However, parts and complete axles for pre-1949 cars remained available for a few years after. In late 1948, the Kaplan Auto Parts Distribution Co. of Cleveland Ohio purchased the Columbia inventory and took over the distribution of axles and spare parts. Kaplan did an active business through out the ‘50’s and into the mid ‘60’s when the supply of key components (new and used) had dwindled and the supply of whole axles was depleted. In 1968, Kaplan scrapped the last of its inventory) and the company closed. 

The first thing a driver had to remember about his Columbia, is that the car must be moving when the Columbia is shifted into overdrive... and also when it is shifted out of overdrive. To shift into overdrive, the dash control (lever on ‘35/’36, knob on ’37-’41, and spring loaded electric switch on ’46-’48) is activated (turn lever to “H”, pull knob, or hold down switch). The driver then takes his foot off the accelerator pedal (to create maximum vacuum) and fully depresses the clutch, which completes the shift. On ’46-’48, the driver also then releases the spring loaded dash switch. To shift out of overdrive, the driver returns the dash control to the standard position (on ’46-’48 the control switch automatically returns to standard position), takes his foot off the accelerator pedal, and fully depresses the clutch, which completed the shift. 

When the Columbia is shifted into overdrive, the sun gear is locked to the differential carrier casting so it cannot rotate. In this mode, the planetary gears rotate around the sun gear and, in turn, rotate the inner gear 28.5% faster than the differential outer case assembly which encloses it. Since the inner gear carries the pinion gears, the net result is a 28.5% reduction in RPM from the differential outer case assembly forward to the engine. 

Shifting from standard drive to overdrive and from overdrive to standard caused a sudden and substantial shocks to the gears, bearings, and housings of the Columbia axle. To absorb these shocks and to lock the sun gear in either standard drive or overdrive mode, the axle has a brake-clutch mechanism called the synchro clutch. The synchro clutch became the weak link of the Columbia overdrive.

Car owners trying to shift out of overdrive without the car moving also caused a lot of problems.

The real design downfall of the Columbia overdrive, is that the Columbia rear end receives about 4 times the amount of torque that a transmission or drive shaft overdrive unit does, due to the fact that it is located downstream of the ring and pinion. The failure point of a Columbia is almost always the internal planetary ring gear which is part of the differential housing. The failure often occurred when the driver attempted to take off from a standing start in low overdrive.

When the Columbia dual ratio rear end was introduced in the early 1930's, most cars had 4 cylinder engines. By the late thirties the V8 had been introduced and the horsepower of cars had more than doubled, which put even more strain on the Columbia rear end. 

So while the Columbia overdrive concept was a good one, the location of the overdrive unit itself, was not. The Borg Warner electric overdrive transmission offered a 33% reduction at engine speed, was factory installed, cost about the same money, and was easier to operate. The Borg Warner overdrive transmission would soon be offered as an option by eleven different car companies.

The local Ford Dealer in Clay Center Kansas, John Mouse Motors ran a quarter page add in the local newspaper in the spring of 1948 offering the "Skyway" Columbia overdrive for $89.50 plus installation. That is equal to $943.00 in 2018 dollars. So when Ford offered the Borg Warner electric overdrive option for $30.00 beginning in the 1949 model year, sales were brisk. 

For reference the $30.00 option is equal to $306 dollars in 2018, so it was no wonder the Borg Warner electric overdrive transmissions sold so well. Borg Warner sold well over three million of the overdrive transmissions by 1960. Studebaker sold the most Borg Warner overdrive transmission options. The Borg Warner electric overdrive was easier to operate and cost about a third of the Columbia option. Within a year of the introduction of the Borg Warner overdrive, the Columbia option was discontinued by Ford.

You will still see a Columbia overdrive rear end under an antique vehicle now and then, and their are now parts being reproduced with upgraded engineering to address some of the original weak points of the original Columbia overdrive rear ends. 

The purpose of this tech article is to give you a little basic knowledge of the Columbia overdrive rear ends so you will know what you are looking at when you see one, and to have a basic understanding of how they work.  Class dismissed!