Jrgunn5150
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I just put this up on the Facebook page, and figured I would post here too for anyone who maybe doesn't go over there.
So the purpose of this first article in the series is to go over the basics of transmissions, how they work, why we need them, and what the different types are. It is a basic article, since it is the first in a series, so if it's beneath your skill level, bear with me.
First off, transmissions, what do they do? Well, the first job of a transmission is to transmit power, from the engine, to the differential (diffs will be covered in another article). The second job of the transmission is to multiply the torque of the engine through gear reduction. The second one is the one we will focus on most as enthusiasts.
Now, why does your beastly big bad engine needs it's copious torque multiplied? It's like this, ever push a heavy shopping cart? It's hard to get moving, but once it's rolling, pretty easy to maintain. It takes A LOT of torque to get a 3500 lb vehicle moving, and 3, 4, or even 500 ft/lbs just isn't gonna cut it. If it did, we would all hook engines directly to the tires and zing down the road at 500 rpm. So think of it like a ten speed, your legs can only put out so much effort and so much speed comfortably, just like your engine. So you have first gear, which is typically somewhere around 3:1. One way to look at it is that it takes your 300 lb/ft of torque, and makes it 900, sweet! Another way to look at it is as a lever. If you need to lift something very heavy, you use a pry bar right? If you have a four foot bar and use one foot to pry with and three to push with, you are using the same 3:1 torque multiplication as the first gear in your trans. Unfortunately, you'll only be able to lift the object one foot. So you shift gears, or levers as the case may be. It's harder to use, but momentum is on your side in a car, it's easy to maintain once you get it started, until eventually you're in overdrive and putting out more driveshaft speed than engine speed, getting great fuel economy and higher possible top speed, while still being able to get off the line quickly.
Let's talk about a few other things now that the basics are down. Why are there so many different versions of transmissions with so many different speeds? Chevy, for instance, can go anywhere from a two speed powerglide to the new 6l60/80e six speed automatic transmissions. So which is better? Race car's use Powerglides, so why shouldn't you? Well, there's more to it than that. Newer model automatic overdrives offer a ton of benefits in comfort, cruising, and economy over older C4's, TH350's, etc. They are also more expensive. But when it comes to drag racing, there's one thing to remember, time between shifts is time lost accelerating. No matter how quickly you jerk your arm, or the valvebody does it?s thing, there's still time where you aren't accelerating, on the dragstrip that's critical, and one main advantage to a 2 speed over a three speed. Another is that the super tall first gear ratio on a 'Glide makes it much easier for high hp nitrous and turbo car's to get off the line without blowing the tires off in a haze. The same reason that a 200r4 or a th350 is better for drag racing in a Gm application, because of the taller first gear vs the 700r4/4l60 variants. Now, driving around, on the street, it becomes more important to keep the engine in it's powerband at part throttle. You're not going from light to light at WOT (probably anyway), you?re just cruising at part throttle. In this situation more gear's has an advantage over less, the newer five and six speeds or going to be able to keep the engine in it's sweet spot easier no matter what the load, throttle position, or speed. This is the reason we are going to start see more and more CVT transmissions in the future as well. CVT?s are constantly variable, and adjust non stop to keep the engine in it's sweet spot.
Hopefully this little article helps out with the basics, the next one will be on converter's and I'll try to take the mystery out of that as well. If you have any questions, suggestions, or corrections, feel free to add them in.
So the purpose of this first article in the series is to go over the basics of transmissions, how they work, why we need them, and what the different types are. It is a basic article, since it is the first in a series, so if it's beneath your skill level, bear with me.
First off, transmissions, what do they do? Well, the first job of a transmission is to transmit power, from the engine, to the differential (diffs will be covered in another article). The second job of the transmission is to multiply the torque of the engine through gear reduction. The second one is the one we will focus on most as enthusiasts.
Now, why does your beastly big bad engine needs it's copious torque multiplied? It's like this, ever push a heavy shopping cart? It's hard to get moving, but once it's rolling, pretty easy to maintain. It takes A LOT of torque to get a 3500 lb vehicle moving, and 3, 4, or even 500 ft/lbs just isn't gonna cut it. If it did, we would all hook engines directly to the tires and zing down the road at 500 rpm. So think of it like a ten speed, your legs can only put out so much effort and so much speed comfortably, just like your engine. So you have first gear, which is typically somewhere around 3:1. One way to look at it is that it takes your 300 lb/ft of torque, and makes it 900, sweet! Another way to look at it is as a lever. If you need to lift something very heavy, you use a pry bar right? If you have a four foot bar and use one foot to pry with and three to push with, you are using the same 3:1 torque multiplication as the first gear in your trans. Unfortunately, you'll only be able to lift the object one foot. So you shift gears, or levers as the case may be. It's harder to use, but momentum is on your side in a car, it's easy to maintain once you get it started, until eventually you're in overdrive and putting out more driveshaft speed than engine speed, getting great fuel economy and higher possible top speed, while still being able to get off the line quickly.
Let's talk about a few other things now that the basics are down. Why are there so many different versions of transmissions with so many different speeds? Chevy, for instance, can go anywhere from a two speed powerglide to the new 6l60/80e six speed automatic transmissions. So which is better? Race car's use Powerglides, so why shouldn't you? Well, there's more to it than that. Newer model automatic overdrives offer a ton of benefits in comfort, cruising, and economy over older C4's, TH350's, etc. They are also more expensive. But when it comes to drag racing, there's one thing to remember, time between shifts is time lost accelerating. No matter how quickly you jerk your arm, or the valvebody does it?s thing, there's still time where you aren't accelerating, on the dragstrip that's critical, and one main advantage to a 2 speed over a three speed. Another is that the super tall first gear ratio on a 'Glide makes it much easier for high hp nitrous and turbo car's to get off the line without blowing the tires off in a haze. The same reason that a 200r4 or a th350 is better for drag racing in a Gm application, because of the taller first gear vs the 700r4/4l60 variants. Now, driving around, on the street, it becomes more important to keep the engine in it's powerband at part throttle. You're not going from light to light at WOT (probably anyway), you?re just cruising at part throttle. In this situation more gear's has an advantage over less, the newer five and six speeds or going to be able to keep the engine in it's sweet spot easier no matter what the load, throttle position, or speed. This is the reason we are going to start see more and more CVT transmissions in the future as well. CVT?s are constantly variable, and adjust non stop to keep the engine in it's sweet spot.
Hopefully this little article helps out with the basics, the next one will be on converter's and I'll try to take the mystery out of that as well. If you have any questions, suggestions, or corrections, feel free to add them in.
