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Reprogram Allison trans
1 st trip In bus was good,The only thing that I would like to do Is reprogram trans to down shift into 5th gear when engine brake is applied instead of 4th gear. When we were on the trip I Googled about this and what I read was factory is set to 4th gear but a lot of people said it was a little agressive for some going into 4th some even did 6th and down shift when you want. Has anyone done this?
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57 Replies
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Ours is set up to not downshift at all. Jake comes on in 6th & I use the pad to manually downshift if I need to. Our previous coach went down to 4th every time I lifted my foot if the jake was on…I like our current setup much better…seems much smoother and not as harsh in traffic. But that said, there are folks who like to really “throw out the anchor” when they use the jake or retarder. One of those personal preference things…like shutting down at the fuel island…or not. 😉
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Ditto what Mike said, mine is 6th and I control as needed. One plus for this setup is when on cruise, the throttle and Jake work together in 6th and is a gentle transition, can’t even feel it.
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I have a retarder, but the downshift issue is the same.
When I had a jake on a previous coach I manually downshifted. There is no downside to doing that because it allowed me to have complete control over what was happening.
The last two coaches have a retarder, and both are programmed to drop a single gear regardless of what gear I am in at the time. This set up has changed how I drive in the respect instead of controlling what gear I am in, I instead control the retarder.
Dropping 2 gears is too aggressive. If you are in 6th but at less than 55 MPH and you lift your foot with the Jake or retarder engaged you are going to get a jolt as the transmission drops to 4th and the engine speed in 6th goes from a little over about 1200 RPM to about 2000 RPM as 4th is engaged.
Now I drive with the retarder selector stick in the “0” position so it is not dropping a gear and engaging the retarder every time I lift my foot off the gas or the cruise control lifts off the gas. As I approach downhills I now manually move the selector stalk to the 2nd or 3rd position, but as soon as I am at the bottom I go back to the zero position. The neat thing about the retarder is if I encounter an emergency stopping situation, as long as the retarder master switch is “on” I automatically get proportional retarder braking assist.
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Does anyone know if that is something that can be changed on the keypad or a Allison dealer has to do?
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You can’t change it on the keypad. A dealer has to plug in to the transmission to reprogram it. Relatively simple; I had it reprogrammed to the way I like it at the first transmission service on the coach.
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My coach was factory programmed to go to 3rd gear when the engine brake came on!
I could not stand it and all I had to do was drive into our local Detroit Diesel dealer. They hooked up a laptop and reprogrammed it to go to 5th gear. I’m very happy now. The whole process took only 15 minutes and the technician can choose any gear you like.
-fred
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I didn’t know when using the Jake Brake that it automatically shifted gears and it brings up some questions.
1. When the Jake changes the transmission to a lower gear, does that lower gear show on the shift window?
2. When the jake brake turns off due to exceloration, does the transmission go back to its top gear automatically?
3. My Jake switch is a two position switch with neutral in the middle and 1 on top and 2 on the bottom. Which number gives the maximum slowing and when do you use #1 over #2?
4. Can you change the Jake from from 1 to 2 or 2 to 1 while in use going down hill and will that also change the gear?
5. When the Jake Brake is used does the rear brake light come on?
My Jake Brake didn’t work when I was driving my bus and is the reason for my questions.
Thanks for your help,
Harry
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Harry,
Not all Jake displays are set up the same. On my last coach I had two displays, one for
the actual gear, and one for the target gear.
I believe newer coaches have gone back to that setup. Target gear when in drive will be 6, target
gear when Jake is on is whatever the transmission is programmed to downshift
to. If you program it to downshift to 5th
when the Jake is on, that is what will show.When you reapply the throttle it will turn the Jake off, and
go back up the gears to 6th as speed allows. Lift your foot, and the Jake will re-engage.Not sure on your coach if 1 is low and 2 is high (I would
think that is the way it would work), but next time you have the coach out,
just try it out—you will feel the difference if the Jake is working right.You can change between high and low Jake settings as the
need for retarding changes down a hill.
It will not have an impact on the gear you are in.Probably most Prevosts are set up so the brake lights come
on with the Jake, but our Affinity was not wired that way. Our brake lights come on with the Jake. Again, you may have to try it out while
someone follows you. -
Harry,
I do not think your jake will change gears. On my 87 vintage coach I had to manually downshift but it had DDEC I so your later ECM may be different but I don’t think so.
1999 XLV X-6872, liberty #440 -
My Jake does not change gears and does not show any other gear on the shift pad other than what was manually selected, such as 6th.
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Jon and Tom,
You are right, the Jake does not change gears, the ECM on the transmission does. SInce you both have the transmission programmed to not downshift with the Jake (retarder in Jon’s case), the transmission will not shift gears with the Jake on. However, if you program it to any other gear–2nd in my case, the transmission will show the programmed gear on the display with the Jake on and throttle at zero, and the transmission will downshift to the lowest allowable gear as speed is reduced, and will shift back up when speed increases.
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Per,
My response was specific to the vintage of the coach in question and I don’t believe the Allison 5 speed had a means of programming a gear change with Jake engagement. What is applicable to the Allison 6 speed may not apply to the older HT755 transmissions.
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Thanks for your replies folks,
We often talked about the use of the Jake on hills. What about in town with traffic, is your Jake on? I’ve read some always have their Jake engaged, do you?
Harry
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Never off.
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Always on … always “high” setting…
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