One of the most enduring motor sport engine and gearbox configurations is the ‘North-South’ mid-engine layout with a transaxle mounted behind the motor. For a manufacturer or a well-funded race team, designing a purpose built or high-end transaxle is not a difficult decision to make. For those of us on limited budgets or ‘green field’ design ability, we are left to pick through the second hand market for something suitable.
The biggest limitation for most second hand transaxles available is the ability to take the sort of power even standard modern engines produce. The next problem is whether they can be adapted to suit the intended purpose. Some can have the diff ‘flipped’ to reverse the direction of drive, and others can’t. The intention of this article is to explore the common options in the marketplace, and to develop an on-going resource as the marketplace changes over the years.
This resource is a list of OEM 2WD INLINE options and will be updated as new information comes to hand. FWD ‘east-west’ gearboxes have not been considered here. This information has been accumulated from internet searches, forums and in rare instances where manufacturers have provided data. Some of the more difficult data is physical dimensions and the amount of torque they are rated to survive. We will gladly update this resource with information from our readers! Take a copy of the attached Excel file, add your own data and we will update this page once the information has been verified.
The layout in which original vehicles used transaxles has some basic variations.
Front Engine Rear Mount – Some cars (such as Porsche 924/944/928 and Corvette) have the transaxle fitted in the rear of the car between the rear wheels with the engine in the front, and connected by a long drive shaft or torque tube.
Front Engine Front Mount – Others (such as the Mercedes-Benz MB100 and most Audis) have the engine in the front with the transaxle mounted directly behind, but still driving the front wheels.
Front Gearbox Front Mount – Then we have the quirky French way of doing things. Renault has for years mounted the transaxle at the very front of the car, with the engine fitted directly behind it. Even the Master van is arranged in this way.
Differential Location – To complicate things further, the diff can be located either at the input shaft end of the transaxle, or at the opposite end of the gear cluster. The upshot here is the difference in length between where the end of the engine will be and where the drive-shafts locate.
Where the intended application is in the opposite direction to the original layout, the direction of drive must be changed. The easiest way of doing this is by removing the differential and reinstalling it upside down. Not all transaxles will accommodate the crown-wheel in the opposite orientation, and where this is the case, the entire gearbox must be rotated and installed completely upside down.
It sounds like a ridiculous solution, but it is very common in the off-road racing world, and in some open wheeler classes. Factors that must be considered include the drain/fill plugs, relocating the breather and possible lubrication problems.
The Main Contenders
To cut a long story short, the obvious options for a modern high power build (say 300kW/500Nm torque) come down to Audi 01E, Porsche and out of left field, Subaru six speed.
- The Audi 01E is difficult to find in Australia, and aftermarket options here are equally limited. There is some confusing information around the strength difference between a factory 2WD version and an AWD version converted to 2WD.
- Porsche’s G50 is still an excellent option and aftermarket support for gear rations, final drives and limited slip diffs are easy enough to find. The gearbox itself is getting rare and thanks to the skyrocketing value of early Porsches, the G50 has risen in price at a similar rate.
- Boxster S ZF six speed is very similar to the unit used in the equivalent year 911, though with the diff flipped to allow for the rear engine layout versus the Boxster mid engine. It’s a tough gearbox with again good aftermarket support, but there wasn’t that many sold on the Australian market and finding one is a bit of an ask. Again, thanks to the rise in Porsche stocks, they too have jumped in value.
- Subaru’s five speed is a good option for low power projects but they shear 3rd gear when any significant amount of torque is run through them. The six speed, however, is a tough unit. Aftermarket support is excellent and they are abundant on the market. Bremer and Subarugears make 2WD kits for them and they can be fitted literally in minutes with the gearbox out of the car. Subarugears make crownwheel and pinions in a variety of ratios and also reverse direction for rear engine projects. The six speed is not all that cheap compared to its glass 5sp brethren, as they are in steady demand from WRX owners but they do represent good value and are easy to come by.
All in all, the modern option for an Australian project builder is probably the Subaru six speed with some important custom additions by aftermarket suppliers.
Commonly Available Transaxles
Here is a list of commonly available transaxles on the Australian second hand parts market, and what we currently know about them. This list is not accurate so use at your own risk, but feel free to provide updated data.
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