In tonight's Seinfeld, the female trucker asks Kramer if he can double clutch. He says yes and screws up the freakin' trans.
What makes a double clutch transmission different from standard transmission? How does it work? Any truckers out there with actual experience? Please post. SS
The is no difference with the transmission. It's just a different way of shifting. Normally when you shift, you press the clutch pedal in once and shift out of one gear into another; for example 2nd to 3rd. When you double clutch, for example from 2nd gear to 3rd, you press the clutch pedal in once to get the transmission out of 2nd gear, release the clutch pedal, press the clutch pedal in again to put the transmission into 3rd. The reason this is done, is usually because there is a problem with the transmission and it won't allow you to change gears with just one depression of the clutch pedal. The problem could be with the clutch, pressure plate, clutch cable or forks. (I don't want to get too technical.) Some trucks have to be double clutched when new,(my fathers 1957 Mack comes to mind) because the trannys weren't right to begin with.
hope this helps, Barrue
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Barrue wrote:
There is if the transmission doesn't have synchro rings! The transmissions on passenger cars (and most trucks nowdays) do have synchros, but there are still trucks whose transmissions don't have them.
I'll explain synchro rings below.
Double clutching is usually done on DOWNSHIFTS, e.g. from 3rd to 2nd, because that's when it's critical to get the revs matched between the input shaft (from the engine) and the output shaft (to the wheels). On upshifts, because the higher gear requires less engine revs, it's easy to let the engine revs drop and then the transmission will easily slip into gear without the aid of synchros.
Not quite. Let's say you're in 3rd and the engine is doing 2000rpm. You want to be in 2nd and you know that will be at (for example) 3000 rpm. Okay, clutch in, shift to neutral. Now let the clutch out fully and rev the engine to a bit above 3000. This is what makes the rev's match. Clutch in again and shift from neutral to 2nd. Clutch out and you're done.
You can do this with any transmission, with synchros or not. It does save the synchros from wearing a little bit. Usually people like to do it because it's fun or because they're driving a Formula Ford. :-)
That, or if the synchros are worn. The synchronizer rings make up for the difference in speed between the gears on the input and output shafts and allow full engagement once the revs become matched.
-Dave
You only have to double clutch on older trucks which did not have a synchronized transmission.
The sequence goes as follows:
Not all that hard. Gets to be second nature after a while.
I knew that time driving trucks would pay off someday.
Ken