sherrycasteen

Exhaust Brake & Lower Gearing

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Yes.  I have to do mine manually, but if yours does it automatically, you can still adjust it manually as you see fit.  If my tranny shifted down to 2nd gear when my Jake kicked in my tranny would be torn out of the chassis at 55 MPH.

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manholt   

I use mine in 5th gear along with brakE when I'm  at 50, then as a slow down to about 30 I turn it off and just use break.  In a city, on city streets I use 4th period.  Have a choice of Hi or Low engine brake. 

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wolfe10   

Couple of points:

The fact that your Allison shift pad window goes from "6" to "2" (or any other gear that has been programmed in for that matter) does NOT, repeat NOT mean it instantly shifts to that gear.  That is the gear TOWARD WHICH the transmission will shift when safe to do so without over-speeding the engine.  Just as when you are sitting at a stop light and the shift pad shows "6".  You are not in 6th gear-- that is the gear TOWARD WHICH the transmission will shift.

And, gearing down RAISES engine RPM, not lowers it.  Your Allison transmission is programmed such that you can not harm it by using the down arrows.  If you down arrow to 2nd at 60 MPH, nothing bad will happen.  The transmission will downshift as it is safe to do so.

The critical thing for driving any heavy vehicle is that the service brakes (brake pedal) is NOT designed to control speed on long descents.  Gears and engine braking is!

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Yes as Brett said it will slow and downshift as needed to get to the target gear. What can happen is if you are going to fast for it to stay in a gear it will upshift to prevent damage. Say you have down shifted to 5th and you still pick up speed it will shift up if your rpm is to hi. This is where you use the service brakes to lower your speed. I find 4th is where I am most when going down steep hills, however on a couple I had to get down to 3ed. In 3ed I have had to give it throttle because it would slow to much.:o

Bill

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FIVE   

As Brett pointed out, we must remember the Allison is smarter than we are.:D  Along the same line, I read on another forum that very recently Allison cranked out their 500,000th 4000 model transmission.

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TBUTLER   

On our coach, I just engage the engine brake and it will downshift automatically as the speed allows.  If it doesn't slow the coach enough, then I use the service brakes to reduce speed.  As it comes into range (RPM) to allow a downshift, it will do so.  I watch the RPM and when it nears 2400 to 2500 for our coach, it is about to shift up to the next gear.  Applying the service brake will keep that from happening if I don't want it.  I have never had to use the up/down arrows to downshift, the Allison 3000 does it all.  One of the keys here is to top the hill at a reasonable speed.  When you see the steep grade sign, ease up on the throttle and coast over the hilltop.  Then engage the engine brake before you start accelerating on the downgrade. 

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