Modern race cars use paddle shifters on their wheels to shift gears, often making a clutch pedal redundant. Of course, this transfers to SimRacing as well. On the other hand, many historic cars feature a manual transmission, often called H-shifter, making the driver do all the work using three pedals and the shifter. But for a short period, an in-between solution was in use – the manual sequential transmission. What is it, and how do you use it in a race car?
SRU has covered H-shifters in another how-to article, but manual sequential transmissions tend to get overlooked. After all, they are just like paddle shifters but using a gear stick, right? Well, this is only partially true, which is why we are going to explain the mechanism and things you should know when driving a car that uses it.
While Formula 1 went from H-shifters to paddles gradually, starting with Ferrari introducing the first shifter paddles on their wheels in 1989, sports cars, rally vehicles and numerous other single-seaters did not adapt the technology immediately. The most prominent examples of this are GT cars and Le Mans Prototypes from roughly 1995 onwards, as well as IndyCars which started using manual sequential shifting slightly earlier than the endurance cars.
The cars still sported a gear lever, but instead of the shifter gate with multiple paths for the lever to go in to select gears, there are only two ways for it to go – for upshifts, the lever is pulled back, for downshifts, it is pushed forwards. The clutch is only needed for starts, it automatically kicks in on upshifts and downshifts.
However, it is not quite as simple as that: While paddle shifters usually have an auto-blip system in place, meaning no throttle input is required on downshifts like it is with a fully manual gearbox, manual sequential shifting usually requires the driver to blip the throttle pedal on downshifts to stabilize the rear of the car – an important bit of technique that often gets overlooked when driving GT1 cars or CART vehicles, leading to unstable cars in braking zones, and even spins.
The reason for this is the same as with H-shifters: Under braking, the engine revs start to drop, and after the downshift, they will rise again while the rear axle is still spinning slower. This means the engine speeds up the axle again, making it unstable. By blipping the throttle, the driver raises the RPM as the clutch is engaged, lessening or completely eliminating this difference in speeds, which makes for a smoother ride. Getting the timing right may seem tricky at first, but can be learned relatively quickly.
As a result, manual sequential shifters can be seen as an intermediate solution between paddles and a manual gearbox. Keeping the need to blip the throttle on downshifts in mind can mean a much more pleasant driving experience and, because of this, faster lap times as well as more consistency. To give you an example, we have embedded an onboard video of Juan Pablo Montoya racing in CART at Laguna Seca in 1999. If you listen to the engine note, you will hear the RPM rise considerably on downshifts as a result of the Colombian using the throttle to match the revs.