What Is the Drivetrain on a Car?

Video Transcript

"We are going to talk about drivetrain a little bit, and drivetrain actually means transmission, and how the power gets to the driven wheels on the vehicle. This happens to be a front wheel drive car, we just talked about transmissions, you can see the bottom of the transmission right here and you can see the bottom of the engine right here. And of course we want to look at the final drive, so the final drive is right out through here and we have two axle half shafts. We have CV joints, an outer CV joint and an inner CV joint right here. And the power is actually transmitted through the transmission. This whole setup actually rotates as you can see. And also is able to change angles. Right now the way the wheels are hanging down because this vehicle is up on the hoist there is no weight on it. But you want to remember this wheel is going up and down, up and down, up and down. So that shaft actually has to be able to move up and down, change it's angle at the same time it's rotating because torque is being applied to that axle to actually rotate the wheel. Now the same thing on the other side right here you have another outer CV joint and you have an inner and what you want to always make sure on the CV joints is that you check the boots because these boots do tend to tear or rupture after a period of time. One easy sign that your boot is ruptured if you notice in the wheel opening which would be right up in here, you'll see grease spatter, you can usually see that on the outside of the car and that's because the CV joint went away. Those can be easily serviced and they are not too expensive. You can even get completely remanufactured axle so this basically is a front wheel drive setup on a vehicle. Ok, so this is a model T Ford chassis, right here the body has been removed and we came out here to actually show you the power train and it really hasn't changed too much. This is a front engine rear wheel drive vehicle, the transmission is actually located right here. And this is actually like the you know the pre forerunner of the modern automatic transmission. This transmission is a two speed transmission but it is engaged and disengaged mechanically. All you have to do on this model T is step down on the pedal. When you push the pedal in, I can do that I'm in low gear right now and when I let it out all the way I'm in high gear, real simple. Parking was also, that controls that too it has to snap back in high gear. If I pull the parking break up, it puts it in neutral if push it forward it's in high gear. If I push down it's in low gear. Ok power is transferred from the transmission to the drive shaft so you see this long tube going all the way back. This is actually a torque tube, these are not used anymore not even in rear wheel drive cars, haven't been really been used since the early nineteen sixties and the actual drive shaft is inside the tube. And then that power goes to the differential unit. And this is the differential unit right here. The differential unit also has a fixed gear reduction in it and the other thing it has to do is transfer power ninety degrees to the rear wheels. :So it actually has to go out to the rear wheels and be transferred so it has to change the direction of power as well as multiply the torque. So whatever the you know if the transmission is in high gear that's usually a one to one ratio, if this has a three to one ratio and the differential you are going to get a three to one reduction. And these are calculated based on the horse power of the engine and the speed and the loads at which the engine is driven so that all takes place. Again this is a model T ford chassis, this happens to be a late model T, late twenties model T and again nothing much has changed as far as technology. It's all pretty basic, pretty much the same. The only thing that we have are limited slip differentials again this will allow greater traction if one wheel tends to slip or slide it will deliver the power to the other. A lot of this has been replaced with electronic systems such as traction control and things like that where we use the brakes to slow down a wheel. It's getting too much power then the power will automatically be delivered to the other wheel. Another thing the differential has to do is what we call differential action, it actually has to allow the wheels to turn at different speeds in a corner. If we weren't able to slow the inside wheel down in a corner and cause the outside wheel to pick up speed the car would hop and bounce around a corner and a lot of people would find that very difficult to deal with."