![]() Notice how the gears on the pinion shaft (lower) reverse direction as the transmission is put into neutral and then reverse. How can this be when you need to shift from gear to gear? The design depends on each shaft having two fixed gears and two gears that run on needle bearings (white arrows) opposite to each other: The 3rd and 4th gear synchronizers are on the mainshaft and the 1st and 2nd gear synchronizers are on the pinion shaft.Ĭonstant mesh means that all the gear sets (except reverse) are in contact with each other at all times. The transmission gears are of the constant-mesh type with balk ring synchronizers. The gearstack is confusing for owners to understand because it's a constant mesh design (a very typical setup). How the gears mate to the shafts and to each other is the really cool part. Those are the basics of power transmission. Drive pinion - (brown) welded to the pinion shaft and connects to the ring gear (not shown) of the differential which drives the wheels. See the Gear Ratios section below for more info.ġ6. This is because 4th gear has a ratio that is lower than 1 and for this reason the 4th gear in all VW transmissions is called an overdrive gear. As we upshift to maintain the rotational speed of the wheels, we need to use successively lower gear ratios because we've lowered the engine speed with our upshift.īy the time we shift into 4th gear, the engine is rotating slower than the wheels. Initially the engine is spinning faster than the wheels (1st gear). The transmission is essentially a torque multiplier: it takes the torque output from the engine and multiplies it at the drive wheels so the engine doesn't have to (nor can it) spin at all possible wheel rotational speeds. Why do these numbers go down as the gear position increases? The gears exist to multiply the torque from the engine to do useful work. Reverse gears - (lime green) located in the differential half of the case, are a set of 3 gears (the extra gear is required to reverse the motion of the mainshaft). Power is transferred from the mainshaft to the pinion shaft via the gearing and this collection of gears and other components is called the gear stack.ġ2. The mainshaft (red) has 4 gears (1/2 of the pairs) and the other 4 are part of the pinion shaft (brown) which is located below the mainshaft. The gear ratio (r) you hear about is the ratio of the number of teeth between two gears (bottom:top) for any set and expressed as ratio:1. There are 8 forward gears paired into sets of two. The red and orange shafts are coupled and spin at the same speed. Mainshaft - (orange) connects to the rear driveshaft (red) by axial stud which is a little difficult to see in the diagram (where red and lime green meet). The clutch has a splined hub with mates up with the splined end of the driveshaft seen in the diagram.ġ0. Rear driveshaft - (red) engine torque is delivered to the transmission via the clutch/flywheel that live in the clutch bell housing (21). Let's follow the transmission of power from the engine to the wheels. I have colored the b&w components I'm going to talk about. You can find the diagram below on of section Transmission and Rear Axle in your Bentley manual (click on the diagram and open it in another browser window for a better view if you wish). Before I can explain how gear shifts are accomplished, let's get familiar with basic components using the same identification numbers in Bentley's cutaway diagram. Of more general interest, is an explanation of how it works its magic as your change gears. The VW transaxle is fascinating study for the compactness of its design. However there is only the briefest of overviews about how the transmission actually works. ![]() Have you ever wondered how the VW 4-speed transaxle works?īentley as always has some nice cutaway diagrams that show how a transaxle combines the features of a transmission and differential into a single case.
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