I am writing this as a general knowledge and use guide regarding the Ford Powershift transmission, available in all North American (and other areas, of course) Focuses. For this guide I will only be focusing on what is available in North America as it is what I am familiar with. The purpose of this is to inform drivers of what they are buying, and to help with any driveability issues (jerkiness, etc.) related to the operation of this transmission. For this guide, I will not be considering the ST model at all, so any reference to the Focus is in reference to the other models (S - Titanium).
Jump straight to post #2 for my recommendations on driving with this transmission and reducing low speed jerkiness.
First I will explain why the Powershift is different then most other gearboxes. Here is a Wiki article on the powershift, for anyone looking for a bit more information on it: http://en.wikipedia.org/wiki/Ford_Po...t_transmission
To start, the North American Focus is available with two gearboxes, a 5 speed manual and 6 speed "automatic" (the Powershift). The 5 speed manual is a typical manual gearbox. The 6 speed automatic, however, is not a typical automatic transmission. If you bought a Focus in North America, and it was equipped with an automatic transmission, it has the Powershift dual clutch transmission. The powershift is what is called a "dual clutch transmission". It's called this because...it use two clutches between it and the engine. For those unfamiliar with how transmission work, here is a very brief explanation of the differences between a manual and (normal) automatic, and how the Powershift is different then either:
- A manual transmission and automatic transmission are designed differently, and transmit power to the drive wheels in different ways. How each gearbox works is mostly irrelevant, but what is relevant is how each gearbox is connected to the engine. With a manual transmission, something called a clutch is used, which operates similar to a disc brake system. What this means is that when the clutch is pressed against the engine, the entire drivetrain (engine to drive wheels) is "locked up". Generally speaking no slipping of any parts happens during this, so any power generated by the engine is transmitted directly to the rest of the drivetrain.
- A "traditional" automatic uses something called a torque converter between the engine and transmission. This is a device filled with fluids, and simply put, several fans (turbines, really). The torque converter allows the engine to revolve without allowing that motion to be transferred to the transmission, and also allows for the engine speed and transmission input speed to be different, even while the vehicle is moving. What this means is that when you are are driving your vehicle, the transmission is not physically connected to the engine (the torque converter does "lock up" at higher speeds though, but that's irrelevant here). What this means is that any changes in engine speed are not directly applied to the transmission (and thus drive wheels), which allows for nice, smooth operation. Think of it like stirring a big pot of water with a spoon. When you first start stirring, the water doesn't really move much, but as you keep going it will start to spin with the spoon and speed up. That is what is happening here, so there is a buffer stopping any jolts from the engine being transmitted to the wheels.
That is important to know as it relates to how the vehicle operates at low speeds. Normal automatic transmissions are notoriously smooth at low speeds because of the torque converter. Manual transmissions often aren't because the clutch does not allow for such forgiveness, and smoothness is directly related to how good the driver is (and how they are able to slip the clutch to keep things smooth). How does this related to the Powershift transmission?:
The Ford Powershift transmission is, in design and general operation, a manual gearbox.
It uses a clutch between the motor and transmission (two of them, actually...hence calling it a "dual clutch transmission"), and the transmission itself is designed internally much like a manual transmission. The differences are in that it has several computer controlled electronic servos (electric motors, basically) that do all the shifting and engaging/disengaging of the clutch. Why does this matter? It matters because it uses a clutch to connect it to the motor, which generally speaking means a bit more of a jerky ride, especially at low speeds (regardless of how good the computer is at operating it).
Why would Ford use such a transmission? Mostly because it offers improved gas mileage over traditional automatic transmissions. Because those transmissions use a torque converter, some of the energy produced by the engine is lost in the torque converter. Meanwhile, a transmission using a clutch transmits all of its power through the clutch so less power is lost overall. This means more power to the wheels, and better fuel economy.