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How should a countershaft brake work

Discussion in 'Trucks' started by jimson, Apr 23, 2013.

  1. jimson

    jimson Well-Known Member

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    I have a Chevrolet C70 with a Eaton RT6610 10 speed transmission. I have questions about how the countershaft brake should work. I know that you only use the brake when stopped to help get the transmission into low or reverse. The problem is it seems like it takes a while for things to stop after you push the button. You can hear the counter shaft slowing down but it probably takes 10 seconds to come to a complete stop. Maybe that’s normal but at a stop sign if you miss slipping it into low it seems like forever.

    I found a drawing of the countershaft brake online. It looks real simple. I don’t have any experience with this so my questions are: Is the function I described normal? If not will rebuilding the countershaft brake help? Where is a good place to find parts? Thanks
     
  2. lantraxco

    lantraxco Senior Member

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    I'm familiar with the term "Clutch brake" Is this what you have, or something entirely different? Clutch brakes usually work by depressing the clutch pedal fully and the brake brings the input shaft to a stop. They do wear and are dependent on proper clutch and linkage adjustment. If it is in fact some sort of countershaft brake just ignore what I said, lol.
     
  3. willie59

    willie59 Super Moderator

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    The countershaft brake described by jimson is an air operated device to help slow/stop turning tranny shafts to assist in initial gear engagement, typically used on trucks with push type clutches that don't use typical pull type clutch brakes. It's a very simple device, air pressure (controlled by button at shifter) pushes a steel rod into the PTO gear of the tranny to slow down turning shafts. You could have a failed o-ring on the piston of shaft brake jimson, pinched or hole in an air line, excessively worn shaft of brake piston, or a bent flywheel clutch disk, all of which would affect performance of countershaft brake. :)
     
  4. lantraxco

    lantraxco Senior Member

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    You see? You never get too old to learn something new! Thanks Willie! :notworthy
     
  5. willie59

    willie59 Super Moderator

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    You're quite welcome my friend. :drinkup
     
  6. td25c

    td25c Senior Member

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    willie59 gave a good description of the brake jimson.I might also add that you need to hold down on the air switch button until the transmission will go in gear.I have seen drivers that will just intermitently push the button a few times only to find the tranny will still grind:D My 1974 gmc has the same setup,it takes about 3 to 4 seconds holding the button down to stop the transmission after the clutch pedal has been depressed.
     
  7. Komatsu 150

    Komatsu 150 Senior Member

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    We had one of those for years on a GMC. It worked fine, never had a bit of trouble with. It still makes me cringe to think of how that stupid thing worked, by pushing a rod into a spinning gear!