Can one gear have more torque?

[Stallion]

I understand that there are gear ratios for each gear in the transmission, but I can't help feel that when I'm in 2nd gear I accelerat better than in 3rd or 1st. Is this just my head playing games? Or can there be more torque in a certain gear?

 

[JohnZ]

Torque at the wheels is simple math - the higher the ratio number of the trans gear or rear axle gear, the more torque multiplication exists when using that gear; you probably like the acceleration "feel" better in second gear, as you can enjoy it longer before you have to shift compared to accelerating in first gear.

 

[Stallion]

Okay, I see what you mean. So you would get max torque in 1st gear, and the least in 4th gear? Provided the rear is constant. Is that even possible? To change the rear gear while in motion? That would be crazy though, because then that would be transmisison theory.

I'm just rambling now. Thanks, John.

TR

 

[Ken]

I have some simple reading for you to do young Stallion. How Stuff Works has a couple of articles you might want to spend a few minutes perusing: How Gears Work; How Gear Ratios Work; How Manual Tansmissions Work and How Automatic Tansmissions Work.

Happy reading and I hope it answers some of your questions.

 

[Stallion]

Thanks, Ken, for the references!

 

[MaineShark]

To further complicate matters, there is also the engine's powerband. The engine makes more torque at some points than others, so a gear ratio that keeps you in the "torquey" area longer will have feel than a gear ratio that keeps you in an area where there is not as much torque. Think of it like running the revs too high before shifting. As you go past the torque peak, you feel like you are losing torque. The same goes for operating too far below the torque peak (although you will get a better feel here, since you get an increase in accelleration, not a decrease).

That's the idea between more and closer gears: to use the rear ratio and transmission ratio, combined with tire size, to keep the engine operating in it's powerband. The more the revs have to drop with each shift, the longer it takes you to come back up to the powerband.

For example, you have a 2.64:1 first gear, a 1.75:1 second gear, a 1.34:1 third gear, and a 1:1 fourth gear (all eventually multiplied by the rear end ratio, of course). That means your revs need to drop 33% when you shift 1-2, 23% when you shift 2-3, and 25% when you shift 3-4.

If you had a '63 Sting Ray with the base 3-speed manual, you'd have 2.47:1, 1.53:1, and 1:1. That would mean a 38% drop on the 1-2 shift, and a 35% drop on the 2-3 shift. The smaller of those two is still larger than the largest of your splits. And that transmission doesn't have as aggressive of a first gear, so it won't give the same multiplication.

The 4-speed allows a smaller split between ratios, and a larger overall spread of ratios. A 5-speed or 6-speed allows even greater variety.

And that's just the fun with manual transmissions. Automatics have the addition torque multiplication factor of the torque converter to worry about (my owner's manual, for example, lists a range of ratios for each gear, to try and give the driver an idea of what the car will behave like).

Joe

 

[Stallion]

I understand, Joe. Would a 6 speed have 2 OD gears then? Or would it just have 1 OD gear but have more agressive first and littlier between the gears?

 

[Ken]

Would a 6 speed have 2 OD gears then?

Depends upon the designer/manufacturer. Six-speeds are available with either one overdrive ratio, as in the case of Richmond's ROD 6-speed, or two overdrive ratios, such as aftermarket T56 6-speeds (5th: 0.80, 6th: 0.62), or the GM T56 (5th: 0.74, 6th: 0.50).

_ken

 

[Stallion]

Okay, thanks Ken! Would 2 OD gears be necessary though? Wouldn't you want a closer ratio for the 6 gears with just 1 OD gear?

 

[Ken]

I really shouldn't pretend to know what I'm talking about here, but I would think that there are a whole lot of variables that determine the appropriate use of gear ratios as they apply to different applications. That is, a gearset that is designed to accomodate emissions and mileage concerns would not be the same gearset one would choose for a racing application.

Then you have different racing applications that could make use of an extra overdrive ratio, whereas others would never find a need for the first, or maybe the second ratio overdrive.

Of course, drag racers would never have a need for overdrive. Heck, they don't even need a fifth gear in most cases.

_ken

 

[Stallion]

Okay, I understand. Thanks, Ken!!