Newbie clutch brake question

You have the function correct. The clutch may just need adjusting, I forgot the exact steps to do it, and it's different for a clutch with a hydrolic linkage, but if you push it all the way to the floor and are still grinding, it should be looked at.

 

My clutch brake hasn't worked since I was assigned my truck. It's not that big of an issue. Let the clutch out at idle, then engage it, put trans in low gear to stop the clutch plate from turning, then shift into 2nd or 3rd to start off.

 

The clutch brake should be about 1/2" from the floor. In other words, if the pedal actually hits the floor, then the linkage is out of adjustment or some part of the linkage is worn. You should have about 2" of free play at the top of the pedal, this is where the pedal is really easy to push the first 2", then hits the clutch bearing and harder to push. As the clutch wears, you'll get less and less free play until it's gone and the clutch starts to slip. To avoid that, the clutch should be be adjusted to get it back to about 2" when it gets to an inch or so.

Another scenario is that the clutch is dragging (not fully releasing), which is a problem with the clutch. Spicer had a run of clutches where the spring pockets broke out and the pieces in the there caused dragging, hard shifting grinds into gear at a stop. To test for dragging, put the truck in neutral on flat ground, make sure that it doesn't roll with the brakes released. Then I set the brakes, put it in gear. With the clutch still to the floor I release the brakes, if the truck wants to roll, the clutch is dragging. Then I pull the cover and look for pieces.

 

Being a driver trainer truck, I'd have to guess that the clutch brake is just plum worn out.

 

Start off in 2nd or 3rd? That is a good way to mess up a clutch especially if you have a load behind you.

 

The mechanics of how to use the clutch brake are correct because it is meant to slow the input shaft down during shifting process.

Proper clutch adjustment is impacted by the condition of the cross shaft bushings. If they are worn out or haven't been greased it will throw off all of the adjustments.

If you look into the clutch inspection plate you should have about 1/2 inch clearance between throw out bearing and the clutch brake itself. This should give you the 1/2 inch brake effect when pressing to the floor.

The free play from released to engagement of the throwout bearing it usually set by having 1/8 of clearance between cross shaft fingers and the throwout bearing. If there is no clearance there it will preload the throwout bearing and cause premature failure.

There are automatic adjusters out there but they have a tendency not to work because of a stuck adjustment ring.

 

So you start in Low gear every time, huh?

60K miles in 9 months running northeast stop-n-go traffic with my methods and my clutch works fine and hasn't needed adjustment yet.

 

Results vary. Not a driver but a mechanic and that was the way I was taught. Taking off in 2 or 3 could cause heat issues and/or broken dampener springs.

I don't start in "Granny" if I am bobtailing, but if I have a trailer behind me (empty or loaded) I do.