Pulled this clip from Best Motoring v5. First up is their "normal" shift which is fast, but the driver in the second shift is so quick he doesn't even lift off the throttle. Simply amazing.

Apologies for the poor video quality.
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Dodge Wiki History

 

That's called speed shifting - drag racers use it a lot. It can help a bit in drag racing, but it's REAL hard on the clutch and driveline.

In a race environment, it can be tricky - speed shifting on a sweeper could lead to loss of traction and loss of control.

Dale

 

I went through 4 clutches in one year on an n/a RX-7 after learning how to doing that! 2 of them were after I swapped the entire drivetrain out for the stronger Turbo II unit. Damn hard on the clutch. On a Bonez aftermarket clutch, the material on one side of the clutch disk completely disintegrated leaving nothing but rivets. The pressure plate doesn't like rivets! Yes it is faster but is it worth the risk in the long run?

 

Yes it is quite hard on the clutch, but when you dont have to pay for the car and your really racing, every shift counts, and your getting paid to mess it up, if your professional or sponsored at least.

 

yup, i was watchin' the Aussie Super V8 Tourers, and they all do that as well, just stab the clutch and *pow* shift, with no lift.

ya just do what you gotta to win.