How many gears do we really need?

General Motors and Ford are ready to join up to develop new 8, 9 and 10 speed automatic transmissions for their cars and light trucks. Working on it jointly will save them loads of dough but how many gears do we really need?

Well, more than we have now if manufacturers are going to meet stringent new federal fuel economy regulations set for 2017.

Back in my university days I got my first 10 speed bike – in fact I still have it. I thought it was a tech marvel back then; but no road bike has 10 speeds anymore and they haven’t for 20 years. Now they’re all 20 speeds and/or 30 speeds. It looks like the same thing is happening with cars.

Automatic trannies with more gears (and more sophisticated electronic controls) are necessary for improving fuel economy. Automakers are downsizing engines and putting in smaller turbocharged versions in order to burn less fuel. These little mills operate at higher speeds to produce maximum output and they need a tranny with more gears to keep the engine running in the sweet spot. On average, an 8 speed automatic can deliver about ten per cent better fuel economy than even a 6 speed ‘box.

Just like with bicycles, the change in car transmissions has come quickly. In the 1950’s the ubiquitous G.M. Powerglide was a 2 speed automatic. Manual transmissions of the day were three speeds with the shifter on the steering column (Three on the Tree). In the 1960s, G.M. stepped up to the 3 speed HydroMatic while little economy cars like the Volkswagen Beetle were considered sporty with a 4 speed manual (Four on the Floor).

Some automatics went to 5 and 6 speeds in the 1990’s with a jump to 7 and 8 speeds for high end stuff in the early 2000’s. Packing more gears into a transmission housing in a big car isn’t difficult. But the problem occurs in compacts and sub-compacts.

First of all, there isn’t much space available under the hood. Secondly, small cars with front wheel drive have the engines and transmissions running across the car, transverse rather than lengthwise – East/West not North/South. The short width between the front wheels determines how wide the trannies can be and that limits the number of gears that can fit inside.

For example, there’s not enough room in subcompacts like the Ford Fiesta and Chevrolet Sonic to jam in a 7 or 8 speed transmission. As a result, they don’t achieve fuel economy as good as the larger Ford Focus and Chevy Cruze which have room for a bigger transmission with more gears. That’s why the smaller the car, the more likely it is to have a CVT - a continuously variable transmission.

A compact CVT with its pulleys and belts produces an infinite number of gear ratios. Some people don’t find them much fun to drive but that’s the way a small, inexpensive car closes the fuel economy gap with larger, more expensive cars with their fancy 6 or 8 speed trannies.

Adding more gears is a way to have both good acceleration and quiet highway cruising with decent fuel economy. More gears, more miles is the rule; it’s not just for “bragging rights.” However the more gears you add, the more mechanical complexity and cost to build it. Plus there’s the annoyance of excessive gear changing if you have too many ratios and the tranny shifts up and down all the time. That’s why they build in sophisticated electronic control systems to keep the number of gear changes at a reasonable level.

So whether you want them or not, they’re coming. Some luxury cars have 7 or 8 speeds now; almost everything will have 10 speeds soon. GM and Ford are about to get busy on it; Hyundai is working on it now. These new trannies will eventually make your current car as obsolete as my 10 speed bike.