This section shall be developed over time to provide information on the drivetrain of the mighty S2. It shall cover the flywheel (and why the ABY has a dual mass configuration), clutch, gearbox variants and some info on how the various differentials work.

If there is a particular subject you would like to see covered in more detail here, then go ahead and send Email !

Read this section first if you need a primer on the workings of differentials.

The 5-speed 01A box, fitted to the 3B engined S2, is the same box as fitted to non turbo 20V (7A or NM engines). It's a good enough box but it is officially only rated at 310Nm though it can handle more torque if you want. Obviously longevity in a hard driven 01A box with a modified engine could be an issue.

Next up came the 6 speed 01E (CGR) as fitted to the ABY engined cars. This is rated for 450Nm and is a much stronger box than the 01A. I know of some tuned ABY engines pushing 550Nm thru these boxes without reported problems. The early variants of the CGR had a weak point on 1st gear but that was fixed mid MY94 and the CRB box on the RS2 is identical to the late made CGR. More details on that to follow. Some drivers don't like the lazier shift on the 01E box - it has a very positive feel, but it won't be hurried. Some owners are fitting 'short-shift' kits to the gear linkages on 01E models to counteract that. More to follow elsewhere.


What preceded the gearboxes fitted to the S2 ?

Taking a step back in time to the 5-speed 016 box, as fitted to the UR quattro and some 100/200 models, and we have a VERY strong gearbox indeed. Earliest versions of the 016 had a lockable centre differential which enabled a 50:50 torque split between front and rear wheels. This is the nearest configuration to what the rally cars used for maximum quattro traction in the 80s. The gear ratio spacing is a bit funky on the trusty old 016, but this a supremely strong gearbox with a light and quick shift. The ultimate version was fitted to the rare 'Sport' quattro IIRC and this is what monster quattros like the Dialynx special runs with. The lockable centre diff was deleted when Audi introduced the MB engined quattros in 1988/89 with a revolutionary system - Torsen.


What's all the fuss about Torsen ?

The later 016, all 01A and all 01E boxes are fitted with the now famous Torsen centre differential - actually so are all true Audi quattros since it was introduced. The VW based A3 and TT use a different centre diff system called Haldex but thats another story. The ingenious 'TORque SENsing' differential is a wonder of mechanical engineering that allows the torque to be split based on the grip available at each end of the car. In normal conditions, the Torsen provides a 50:50 torque split but in the event of loss of traction at the front wheels, torque is shifted to the rear (and vice versa). It is this transition from 50:50 split to a maximum bias of 70:30 either way that makes the Torsen equipped cars rather tricky to drive thru an understeer situation (in the wet for instance) to one of controllable progressive oversteer by using the throttle pedal. This is the art of 'Torsen-ing' a quattro when driving on the limits of traction. Not for the faint hearted ...

Another flaw with the Torsen device is that it cannot be locked by the driver - as in the old URs.

True quattro aficianados will argue that the original full time 50:50 split on the non Torsen gearboxes is the ultimate configuration for handling - especially on rough or slippery terrain. But for civilised use by the masses, the Torsen system is arguably better for everyday use as the dynamics of a front heavy Audi provides a natural tendency to understeer in corners on the limits of traction. The gut reaction of most drivers in such a situation is to gently lift off the gas and so understeer is reduced.

Torsen equipped quattros are generally accepted to be harder to drive on the limit than a non-Torsen quattro because of the counter-intuitive way in which the driver has to provoke oversteer on a Torsen system. Nuff said !