History: When most cars were 6-cylinders and the cubic inches hovered around 230, passenger car gear ratios were usually from 3.70 to 4.30. Most people of the time considered 70 to be really "stepping out" and average highway speeds were around 60mph. Most manual transmissions in use had been developed in the 1930s and had synchromesh in 2nd and 3rd. As time went by, 1st gears were also synchronized in most, although Mopar 3-speeds had an unsynchronized First gear until the '70s.

When American OHV V8s were developed, they were most often put in front of the 3-speeds of the day. Because they had more power, people could drive faster and so overdrives were added to the 3-speeds for cruising on the new highway system of the time, the Interstates.

The first American V8 to have a 4-speed available was, IIRC, the 1957 Corvette. If you asked most American car designers of the time they'd tell you a huge torquey V8 didn't need more than three speeds, it could accelerate very well.

Remember that most automatic transmissions started out as 2-speeds, the 4-speed Hydramatic being an exception. I believe that that transmission used First as a starting out gear, and unless you came to a complete stop it didn't engage after the car started rolling.

I believe Chrysler Corp's first 4-speed in a car was in the early '60s and was imported from France.

There were truck 4-speeds, but they were really three speeds with an ultra low "granny" First gear and were too big and clumsy for automobile use.

As the horsepower wars raged in the '60s, Ford and Chrysler designed some really bulletproof transmissions. GM used the wimpy Saginaw and the medium strength Muncie, which was never as strong as a Ford Toploader or A-833.There was also the Borg-Warner t10, which was about as strong as a Muncie until the Super T10 was developed in the '70s. But my bigblock chevy friends gravitated to the "Hemi 4-speed" as the only 4-speed that wouldn't puke behind a 433 or 468.

At the time it would have been nice to run an overdrive on the street, but no-one did, to my knowledge. It was considered a "badge of honor" to be driving down the highway at 70 with the bigblock screaming in front of the 4.56 gears popular at the time. It didn't make for happy cruising. And there were no overdrives or overdrive transmissions that would work.

What really changed things were the energy crises of the '70s and early '80s. Also as engines got smaller and wimpier again, five-speeds started to come into fashion.

At this point I must mention the Doug Nash 5-speed, which was an interesting design concept. If you study gear power losses, you come to the conclusion that a 4.56 rear gear wastes a lot of energy. There is a lot of friction in a hypoid gear setup. So Doug Nash designed a 5 speed transmssion with a 1:1 Fifth gear, and a 3.something to one First gear. It was intended to be used in front of a 3.07 or 3.23 rear. More gear reduction in the transmission starting out, with less friction in the driveline in Fifth. For some reason that idea never really caught fire.

So now most everything has a medium rear end ratio and a 0.67 - 0.80 Fifth or Overdrive gear.


One important thing to bring up:
the Norman de Laycockville overdrive that was vary popular on European cars and was available on the Volvo 144, 244 etc, is the same overdrive that is now sold as the Gearvendors. The materials have been beefed up, but the overdrive design is the same. There is an oil pump that operates off the input shaft. When the overdrive is engaged, the oil from the pump either locks or unlocks a clutch pack to make the OD work.
My friend had a 75 245, and one day he was all bummed out as the OD wasn't engaging. We dropped the pan, cleaned the input screen to the pump, added new fluid, and it worked again. My friend was impressed. I was impressed that a 4-cylinder Volvo had a manual transmission as physically large as the GM Saginaw 3 or 4 speed.

The Gearvendors unit has been much improved over the years, and it hasn't developed a reputation for failure, so it must be beefy.

R.