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Dec 13

Transaxles

This is the first in a series of light technical articles by Michael Adams. We will endeavour to post at least one of these per week. If you have a specific topic or car component that you’d like to see discussed / explained, please let us know.

If you’ve been following the V8 Supercar Car of the Future information the way I have, you may have noticed that one of the changes being made in 2013 is the introduction of a Transaxle unit to the car. Unsure of what a transaxle is or what it does? Keep reading.

The Transaxle is actually a relatively simple concept and a humble component development. The name of it basically gives the game away, with “Trans” from transmission and “axle” from axle. Pretty clever, hey?

To put it simply, a Transaxle is the combination of the gearbox, differential and drive axle(s) into one unit. But why would you do such a thing in the first place? What’s the point of combining them?

When you have the engine at the same end of the car as the driven wheels, a Transaxle is the most efficient way of packaging all the required components into a limited amount of space. It’s obviously less of an area hog than spacing the driveline out along the length or width of the car in the traditional engine-transmission-diff way would be.

The original Morris Mini was a classic example of clever packaging via Transaxle and the lessons learnt from it’s layout and design are still being utilised to this day in front-engine, front wheel drive cars.

The ability to put the engine, gearbox, diff and axle into a car as essentially one unit is also the reason that rear-engined rear drivers (Beetles and their ilk) and exotic mid-engined machinery, such as that from Italy, also make use of a transaxle. It’s just easier to install.

Obviously with a mid-engined car, you can understand the want to maintain good levels of weight distribution as that is why it was produced as a mid-engined vehicle in the first place. Again, a transaxle makes sense for this reason, because it puts all of the weight from separate components into one “lump” next to the motor.

Even when stuck with a front-engined layout, many car manufacturers have solved weight distribution issues via Transaxle usage. The Porsche 944 and Alfa Romeo’s classic GTV series as a couple of examples. These used the Transaxle in the rear to counteract the weight of the engine up the front.

In a V8 Supercar, all of this will be fine. In road cars, there are some issues with the Transaxle rear/engine up front configuration. Sure, you get an increased sense of balance in the handling. But you also get a prop-shaft that runs from the engine to the transaxle that must spin at the same speed as the engine at all times. Even when you’re just tooling around down at the shopping centre car park.

You also need excessively long linkages to run from the gearstick between the seats to the gearbox down at the rear diff. This is why Porsche 928s for instance, often have huge issues with manual gear selection, especially when old and tired.

Conversely, the Ford RS200 Group B rally weapon ran a mid-mounted engine with the Transaxle placed in the front of the car with a direct feed to the front wheels and a prop-shaft running back to the rear wheels.

So there you go, a brief summary of Transaxles and their usages.

Cheers,

Michael Adams from Test Driven Australia
Article originally written for Infinite-Garage.

3 comments

  1. Popolac

    Soooo, a Transaxle is when Axle Foley dresses up like a woman, right?

    1. pistolpig

      Lol! Nice one.

  2. project7

    Nice stuff, guys. Today I learned the 944 and Alfa GTV were transaxle rides..

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