The clutch with a brake is a new one to me. It seems like a truck having that kind of clutch needs to be shifted without the clutch. How new to the market is this type of clutch, as I have never heard of one. Is it's main purpose to prevent grinding when stopped and going from neutral to first?
Bill
Pull type clutches with clutch brakes are quite old, very old actually, my 1925 Mack AC had one.
A normal automotive clutch is push type, the throwout bearing is pushed forward against the fingers of the pressure plate to disengage it.
this is a picture of the throwout bearing (but not totally correct, as it has the wrong input shaft bearing retainer and input shaft.)
[IMG]http://thumb9.webshots.net/t/69/469/4/22/46/2270422460080251109ThOpat_th.jpg[/IMG]In a big truck with this type of clutch and a transmission with a lot of rotating mass they will often have a "counter shaft brake" essentially it is an air cylinder that is forced into a PTO gear to slow it down by friction, the momentary pushbutton to operate it is mounted on the shifter and has air lines on it. I installed one of these on a truck I had, worked great at stop lights. When warm the transmission could take 10 or 15 seconds to stop without it, long enough that people would blow their horns at you, stopped in seconds with the brake.
Many big trucks, and almost all semi trucks have pull type clutches. The throwout bearing is actually assembled as part of the pressure plate, and the "fork" pulls the throwout bearing back toward the transmission to disengage it.
If it is equipped with a clutch brake the clutch brake disc that is keyed to the input shaft will be squished between the stationary input shaft bearing retainer and the throwout bearing, thus stopping the input shaft, clutch, and counter shafts from turning.
Here is a picture of a pull type clutch and the throwout bearing.
[IMG]http://thumb9.webshots.net/t/69/469/4/18/90/2838418900080251109kpCRzW_th.jpg[/IMG]A clutch brake "(or counter shaft brake for that matter) is not to be used while driving, only when putting it into gear when you are stopped. So for a clutch brake you never fully depress the clutch when shifting through the gears, as fully depressing it engages the clutch brake.
Grigg
