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Skykingtcb

Pac exhaust brake operations

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Hello

2003 Monaco Diplomat 40 DST Cummins 8.1

I bought this coach used and never used a pac brake before. Have read the very brief info in the coach master manuel also searched this site.  I don't think I am using it correct. The speed continued to increase going down Cuesta grade near San Luis Obispo. Could someone give my some pointers on pac brake operation? What speed do u start at? shift down first to get rpms up ? 

Please help I feel like a FNG

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I downshift into 5 first, then put mine on, most times I need to give some gas to maintain speed.  Real steep grade, with turns...when you brake, the gear should drop down on it's own...if not, push on down arrow until you feel comfortable with the speed.

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The Pac Brake assists the compression to slow you but you still need to slow down and gear down before the hill 

So start out slow and gear up as you learn what grade each gear will work on 

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Use the "down arrow" along with the pac brake to maintain your speed.  If you are speeding up, use the brakes firmly enough to allow you to down arrow to the next lower gear.

Your equilibrium speed will be faster than a loaded 18 wheeler, slower than an empty one-- straight physics.

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9 hours ago, desertdeals69 said:

When I turn mine on the set gear goes to 2 and actual gear is dependent on the vehicle speed.

Correct.  The Allison will be programmed with the "pre-select" gear TOWARD WHICH the transmission shifts.

2nd and 4th are popular choices, but an Allison dealer can program it to whatever you want.

As desertdeals69 said, that does NOT mean that is the gear you are in-- any more than it showing "6" when at a stop light means you are in 6th.

You have to slow down enough that it will not overspeed the engine for it to drop to the next lower gear.

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16 minutes ago, manholt said:

Yeah.  Mine is a little different, as I have 2 toggles...one for high only and one for high/low engine brake!

 

Yup, an engine compression brake is entirely different than an exhaust brake.  And, most engine compression brakes do come with a low/3 cylinders doing it and high/all 6 cylinders doing it. They are also known as Jake brakes.

Exhaust brakes are found on smaller diesels.

Engine compression brakes are found on larger diesels-- starting with the Cummins ISL 8.9 liter which was offered either with exhaust or engine compression brake..

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After reading the above posts I learned to use the pac brake. I now plan ahead better at start of the downhill flip the pac brake switch on slow down for it to downshift. 

 

Thanks to everyone for the advise

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Yup, use of the exhaust brake switch AND the "down arrow" and in some cases the service brakes to slow you enough to drop to the next lower gear ARE part of learning to drive a heavy vehicle.

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