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Speed shifting

Hey Boys, love the show. I just bought a new 2009 Mazda 6. Great car. I am curious about the value(or damage)of speed shifting, (ie changing gears without using the clutch.) If I do it at the correct RPM’s it is smooth as glass. Does this save on clutch life or is it just too risky and damaging to perform?

Speed shifting is changing gears without lifting your right foot off the gas, not what you are doing. It’s what drag racers do to get maximum acceleration. They also rebuild their engines, transmissions and clutches after a few races.

You are just timing your shifts as to not need the clutch to disengage the engine from the transmission. If you time it right, you may not do much damage – buy why risk it? Clutches are easier (and cheaper) to replace than transmissions.

A buddy and I drove his MGB from Boston to FL during our college days (mid 1970’s). The clutch cable snapped about 1/2 there. We drove the rest of the way by timing our shifts – rolling starts were the only hard part.


If you time it right you won’t damage anything. if you grind the gears you may damage the transmission, but not using the clutch will cause no damage whatsoever to the clutch.

Shifting without the clutch is not, however, referred to as speed shifting. Speed shifting is what twotone explained, shifting very quickly, without lifting off the throttle. Speed shifting is VERY hard on the clutch.

Shifting without the clutch isn’t a very good practice even when you don’t “crunch” the gears. My wife broke her left foot, but still managed to use the clutch. She couldn’t get enough leverage with one crutch, so she used both crutches on the clutch. This is called “double crutching”.

Use the clutch pedal. You bought a manual transmission–the clutch is there for a purpose.

I’ve never been able to figure out what is so difficult about depressing a clutch pedal, but apparently it must be. I remember riding in a 1949 Packard that had an electric clutch. As one moved the gearshift, an electric solenoid disengaged the clutch. The clutch was again engaged when the car was in the next gear. As I remember, the system was rather troublesome and most people turned it off. About the same period, Hudson had its Drivemaster–a system where the clutch was disengaged and then engaged using a vacuum cylinder. I think many Hudson owners had the Drivemaster disconnected. Volkswagen in the late 1960’s introduced the “automatic stick shift”. The car was shifted manually, but there was no clutch pedal. It took more money than the gross national product of two third world countries to maintain this system.

The Borg-Warner automatic overdrive had free-wheeling below the overdrive kick-in point (about 30 mph) if the overdrive was engaged. These cars could safely be shifted without using the clutch.

I have done it twice. Each time the reason I did it was a broken clutch cable. I did manage to get home without damage, but I don’t recommend it.

It’s your car and when you damage the transmission, you will have to pay for a new one. They will be able to tell you deliberately damaged your transmission, so it won’t be covered by any warranty.

I say do it until it ruins the transmission. It is your money to waste.

Follow up – you will not grind your gears (they are always engaged) but you will wear out your synchros. These are the cone-shaped “gears” which match the speeds of the input to output shaft gears. It’s the dogs on the sliders which engage into the gear splines. Just a more technical way of saying “use the clutch”. Or, trade it in and get an automatic.


Motorcycle transmissions are quite different than car tranny’s. On motorcycles you can install a button which is in effect a switch to turn off the ignition for an instant. Hit the button with a bit of upward toe pressure and the tranny slips into the next higher gear. Downshifting is done the old fashioned way with the clutch.

With a car you have to lift up on the gas for an instant and move the gear selector to the next higher gear in effect doing the same thing, but the shift doesn’t maintain power as well in a car compared to a high powered sport bike.

If you really want to shift without losing power in a car you time the quick push on the clutch with the throw of the shifter without taking your foot off the gas at all. This is why Hurst shifters were such sturdy units in the old muscle car era.

Fast shifting of any sort is likely to cause wear and damage to the clutch, transmission, differential, and any other parts of the drive train that take the hit of power and torque that send shock waves through out the drivetrain. These techniques aren’t subtle, they are in effect car brutality but the dragsters and race cars that employ these practices are designed for such abuse and in time rebuilds are expected as a cost of racing. If you wish to use these techniques on a street car fine, but you can expect to pay the price at some point when something breaks.

It occurred to me this morning that what you are doing isn’t speed shifting. Truckers call this “floating gears.”