How the Transmission Works in a Jaguar S-Type

Written by john albers
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How the Transmission Works in a Jaguar S-Type
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Manual Jaguar S-Type Transmissions

Manual Jaguar S-Type transmissions work much in the same way that any other manual transmission functions. It sits between the driveshaft and the engine's flywheel, with the clutch assembly sandwiched between the flywheel and the transmission. Inside the transmission there is a crankshaft with multiple gears threaded on it. The stick shift controls the placement of the crankshaft, whose far end connects to the driveshaft by means of a universal joint. The flywheel is connected to a gear that spins at a 1:1 ratio, while the crankshaft connects one of its gears to the aforesaid one. Energy comes from the engine through the flywheel, through the 1:1 gear, and drives the crankshaft, which in turn drives the car's wheels. When shifting, the clutch pulls the gear away from the engine's flywheel to momentarily cut power. The stick shift moves the crankshaft and changes which gear set along the crankshaft is resting against the 1:1 gear, changing the car's range of speed when the clutch is let back in.

Automatic Jaguar S-Type Transmissions

The automatic transmission of the Jaguar S-Type is very complex. It relies on a series of gears that sit inside one another called planetary gear sets. The S-type has three of these sitting in line in front of the engine's flywheel, connected to one another, then leading out to the driveshaft, which leads to the drive axle, which makes the wheels turn. Within each planetary gear set is a number of brake actuators and clutches, which, when engaged, allow some gears to turn and hold others still. This system of brake actuators and clutches is controlled by a hydraulic mechanism called the valve body, which responds to the engine's rising rpm by changing the configuration of engaged and disengaged clutches and actuators. Because of the way the planetary gear sets sit within one another, they are capable of producing mechanical energy (movement) at varying rates. So the engine starts out by turning the flywheel, which turns the planetary gear sets, unfettered by the valve body, to produce the car's low-speed first gear setting. Eventually the valve body engages, changing the power ratio the planetary gear sets produce, bringing the car into second gear. This happens again and again until the car is at top speed.

Semi-Automatic Jaguar S-Type Transmissions

A semi-automatic transmission is also known as a dual clutch transmission. It's considered the best of both worlds, allowing for automatic driving or manual driving without having to depress a clutch pedal to shift gears. The design is similar to that of a manual transmission, but with a few additions. Instead of one crankshaft, there are two, one sitting inside the other. Instead of one clutch, there are two, one controlling the one crankshaft, the other controlling the second crankshaft. Each crankshaft controls a set number of gears. Shaft 1 controls the odd-numbered gears, shaft 2 controls the even-numbered gears. Starting from first gear, shaft 1 is set on the first gear as normal, while shaft 2 is hovering over the second gear. The ECU, or engine control unit, monitors when it's the best time to shift gears, engaging the two clutches electronically. The clutch controlling shaft 1 engages, pulling the shaft away from the first gear and leap-frogging it to hover over the third gear, while the clutch controlling shaft 2 releases, putting the car into second gear. This leapfrog process continues as the car accelerates. The driver can also force the car to switch gears when he wishes by using paddle controls set into the car's steering column. This overrides the ECU and forces it to send the signal to the clutches to change gears.

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