Now that we know the Pac brake how about the trans

[shirlock1]

That was a good discussion on the Pac brake but I am baffled on the transmission gear indicator. Why would the indicator go to 2 when you take your foot off the throttle with pac on. I would very much like to have my display show the gear you are actually in. I think that it would be much better on hill management than to show the target gear. Can anyone tell me if there is a way to do this. Also while we are on it, is there an explanation of the economy mode?

[FlyingDiver]

It depends on your model of transmission. Ours shows both the current gear and the target gear.

Economy mode changes the shift points slightly to "improve" fuel economy. I've never bothered using it.

Do you have the manual for your transmission? Mine was in the big Spartan chassis binder when I picked up the coach. If not, you might be able to get one from the Allison website.

joe

[Route 66]

You will need to ask Allison if your single digit display can be reprogrammed.

When Allison switched from the dual display to the single display, there were countless complaints and Allison switched back to the dual display, in most cases I believe.

[Flagelpater]

According to the answer I got from Allison, a couple of years ago, Monaco was the culprit. They did not spend the money for the dual gear display unit. I would like to think the INFO was there, how do we display it is the question.

[a k]

Get a QC5100 handheld computer from Cummings. You don't have to guess at anything then. Reads all engine, trans, functions ,faults and trips. Plug it in as you go down the road. Want to know what the fault code is? This little computer will do it.

[shirlock1]

That sounds like a great idea, but I have a cat engine. Does anyone know if there is such a piece of equipment for a Cat?
Jim

[Norm4015]

The PAC Brake or Exhaust Brake is programmed by the chassis manufacturer to specifications of the motorhome maker. The brake can be programmed to gears 2,3,4, or 5, but it is usually programmed to either 2nd or 4th gear. A Cummins, CAT, Freightliner or Spartan service facility can program it to any gear you desire and even set it to not select any gear allowing the driver to manually select a gear of choice.

When you apply the exhaust brake it will show the target gear in the display, but does not immediately down shift to that gear. It down shifts one gear at a time according to engine rpm and it will never cause damage to the engine or transmission. Just as when you place the transmission in Drive it with show 6th gear in the display, but works its way from 1st gear to 6th gear, the exhaust brake will show say 2nd gear, but will start down shifting from 6th gear.

Allison makes single and dual displays and it is up to the motorhome maker to specify which one to install. Of course, the single digit display is cheaper and is often ordered. But I think every display should have two digits - the target gear and the actual gear. My motorhome has a one digit display, but I run a Silverleaf VMSpc which shows both actual and target gears along with much other information.

The Economy or Mode button selects a different shift pattern to save fuel. The transmission will up-shift at a lower rpm that keeps the engine in its best horsepower/torque band. So you will take off slightly slower, but will save fuel. And when you are in 6th gear and slowly dropping speed the transmission will stay in 6th gear longer to save fuel. When not in Economy Mode my transmission will drop into 5th gear at 52 mph and in Economy Mode it will hang in 6th gear down to 48 mph.

If you drive in rolling hills and your transmission continually shifts 6-5-6-5-6 then your transmission is "hunting gears" which is hard on your nerves and damanging to the transmission. Put the transmission in Economy Mode and it will likely hang in one gear and quit hunting. The default when you start the engine in Economy Mode OFF so you have to press the Mode button each time you start the engine to turn it ON.

[Flagelpater]

Thank you very much Norm. That helps a lot. Do you also know what the Exhaust brake Max Engine RPM would be if the Transmission was Not programed by the manufacture? My No Load RPM is 2200 with the EB On.

[Norm4015]

The engine rpm with the exhaust brake turn on depends on the engine and even on the year of the engine. Whether the exhaust brake is programmed for 2nd gear, 4th gear, or not programmed to any gear makes no difference on the engine rpm during activation of the brake.

The smaller the engine the higher the maximum rpm will be with the exhaust brake on. An ISB engine will have a max of 2700 rpm while an ISX will have a max of 2000 rpm. I have a 2005 ISL and the max is 2500 rpm. These are general speeds and they will vary slightly with the year of the engine.

[Flagelpater]

My 05 Knight with the 330 ISC is limited to 2200 RPM. I had a 04 with the same engine and it went to 2600 RPM. This is why I was thinking it may not be programed properly. As soon as it reaches 2200 RPM it shifts Up and then there is almost no Exhaust Brake effect. Could I manually shift to a lower gear and be responsible for the RPM myself? Do these symptoms relate to it not being programed properly?

[Norm4015]

Quote:

Originally Posted by Flagelpater My 05 Knight with the 330 ISC is limited to 2200 RPM. I had a 04 with the same engine and it went to 2600 RPM. This is why I was thinking it may not be programed properly. As soon as it reaches 2200 RPM it shifts Up and then there is almost no Exhaust Brake effect. Could I manually shift to a lower gear and be responsible for the RPM myself? Do these symptoms relate to it not being programed properly?

Shifting up at 2200 rpm in your ISC engine seems like that is too low of a rpm and as you said, when it upshifts the engine rpm will drop and the exhaust brake won't be very effective. You can try pressing the down arrow to try to hold it in 4th or 5th gear, but if the ECM says to shift, it will shift anyway. You can manually place it in 3rd gear but the transmission can go to 4th, 5th or 6th on its own.

It could be the program and that might be hard to prove. You can call Cummins and they can give you the specs, but the program was set by Monaco and I don't know if you can get much help from them. A GOOD Cummins shop may be able to look at the program with a computer connected to the engine and make a change if needed.

[Flagelpater]

Thank you Norm. I will try that and let you know what I find out. I am not trying to get Monaco to fix it, just trying to figure it out so I can take it to the correct place. Looks like Allison will be the best direction to go.

[Batman_777]

My owner's manual states the Exhaust Brake must periodically be used or damage can occur to it that is not covered under warranty.

Sometimes I feel it you sneeze and something breaks the next day, it's not covered under warranty.