Transmission & Drivetrain

Is your clutch slipping now that the engine makes more power, or do you need to put the power down to the wheels more effectively? The drivetrain is everything that transfers the engine's power: clutch and flywheel, gearbox, driveshaft or chain and sprockets, differential, transfer case, bearings and shifter. This category is for you if you maintain, upgrade or build a project for road or track.

The entire drivetrain has to keep up

Every part of the drivetrain must be able to handle the torque the engine delivers. If you increase power with higher boost or other tuning, the clutch is typically the first thing to start slipping, but the gearbox, axles and differential are also put under more load. So look at the whole chain of parts when planning a project, so the weakest link doesn't hold back the rest.

How to choose a clutch and flywheel

Among clutches and flywheels, the torque rating of the clutch is the first criterion, but how you use the car matters just as much. In this category you'll find brands such as SPEC, Action Clutch, Clutch Masters and ACT, with ACT, for example, offering race discs with both 4 and 6 pucks in sprung and rigid versions. Consider in particular:

• Friction material and number of pucks: fewer pucks typically give a more aggressive engagement, which can make pulling away less smooth.
• Sprung or rigid disc: springs in the hub dampen vibrations; a rigid disc is simpler but can cause more noise and driveline shock.
• Flywheel: a lighter flywheel can let the engine rev up faster, but can make the car more demanding in city traffic.

Chains, shafts, differentials and shifters

Under driveshafts, chains and couplers you'll find chain and sprocket kits, among other things, e.g. from Vortex Racing. Here the chain pitch (e.g. 525 or 530), number of links and tooth count must match the vehicle. Changing the tooth count changes the gearing and therefore acceleration and top speed. A limited-slip differential can improve traction out of corners, but the type determines how the car behaves and which oil is required. A short shifter can give shorter throws between gears, depending on the gearbox.

Installation and maintenance

Fitment depends on car model, model year, engine and gearbox, so check the part number against your car. It's a good idea to replace the release bearing and pilot bearing at the same time as the clutch, and have the flywheel inspected. Chains must be lubricated and tensioned according to the manufacturer's instructions. A rumbling or humming noise that follows road speed can be caused by worn wheel bearings and seals.

Frequently asked questions

What is the difference between a sprung and a rigid clutch disc?

A sprung disc has springs in the hub that dampen vibrations and shocks in the drivetrain, and is typically more comfortable on the road. A rigid disc is simpler and lighter, but can cause more noise and a harsher engagement.

How do I know if my clutch needs replacing?

Typical signs are revs rising without the car accelerating accordingly, a smell of burnt friction material, or the clutch biting very high in the pedal travel. Judder when pulling away can also be caused by a worn flywheel.

Should the chain and sprockets be replaced at the same time?

This is typically recommended, because a new chain on worn sprockets, or vice versa, wears faster. Check the chain pitch, number of links and tooth count so the kit fits your vehicle.

Do drivetrain modifications require approval for road use?

It depends on the product and the car. Changed gearing or a different gearbox can, for example, affect the speedometer reading. Always check the requirements and documentation for the specific part number before fitting the part to a car used on the road.