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EasyDoesIt · 04-08-2008, 03:56 PM

I have just taken possession of a 1998 Winnebago Chieftain with a Cummins 275. I know the 275 is not the powerhouse some of the newer coaches have BUT. I find that I cannot run the coach on cruise control with the selector in 6th gear as it will slow down to under 1400 rpm before downshifting on any grade. Even in 5th I must manually downshift if 4th is required. It seems to shift properly when not on cruise control. Is this normal or can it be reprogrammed?

EasyDoesIt · 04-08-2008, 03:56 PM

I have just taken possession of a 1998 Winnebago Chieftain with a Cummins 275. I know the 275 is not the powerhouse some of the newer coaches have BUT. I find that I cannot run the coach on cruise control with the selector in 6th gear as it will slow down to under 1400 rpm before downshifting on any grade. Even in 5th I must manually downshift if 4th is required. It seems to shift properly when not on cruise control. Is this normal or can it be reprogrammed?

wagonmaster2 · 04-08-2008, 05:19 PM

My only guess, judging by most cruise controls I've owned, is that the cruise control is not applying the throttle enough to keep up the set speed until the vehicle slows down enough that the throttle is applied heavily enough for the transmission to know its time to downshift. Whether or not the cruise control can be adjusted to keep the actual speed closer to the set speed, I do not know. Sorry.
Wagonmaster2

Pusherman · 04-08-2008, 05:35 PM

I'm not familiar with your coach and tranny setup, but it sounds like it's programmed to work in the 'economy' mode, where it downshifts at lower rpm's for improved fuel economy. You might want to call Allison to see if it can be reprogrammed to downshift at a higher rpm.

Matt-n-Dede · 04-09-2008, 04:37 AM

I have a 2000 Chieftain with the same motor and trans. Mine will shift about the same whether in cruise or not. One annoyance I have is that on certain long grades while in cruise, it will changed from 6th to 5th back and forth every few seconds so I usually just press the petal to the floor until I crest the hill.

Matt

Gary RVRoamer · 04-09-2008, 05:46 PM

I would discuss the problem with an Allison shop - I would think they could program around it. But the problem appears to be the cruise more than the transmission. Maybe some diagnosis on the cruise is in order before changing the Allison programming.

tom wilson · 04-10-2008, 08:29 AM

my cruise control will not pull the throttle to wide open throttle causing the same problem you described. you can have the cruise control tightened up or just do as me and others do..just mash the throttle with your foot when you want it to downshift.

EasyDoesIt · 04-10-2008, 12:35 PM

Thanks for your replies. I can mash the throttle to the floor with no downshift change until I disengage the cruise control. It appears to me that the transmission has a different program for cruise control. My unit does not have a functioning mode control as far as I can tell. Just a gear selection indicator. Punching the mode button does not seem to do anything.

EasyDoesIt · 05-04-2008, 02:58 PM

You notice I started out this thread by stating the 275 did not have a lot of power. Well, I took it in to the Cummins service center here in the twin cities and the found a loose clamp on the charge air circuit. NOW I have plenty of power and the tranny works fine on Cruise Control. That's nice when you fix one problem and it fixes two!

Gary RVRoamer · 05-04-2008, 04:40 PM

Glad to hear you got more power and a better working cruise!

gmanatl · 07-27-2008, 07:02 AM

Congratulations on your Chieftain. We bought a 1999 Chieftain with the 275 ISB and Allison 3060 6 speed about 18 months ago. Contrary to what someone said I notice quite a difference when economy mode is engaged or turned off. Especially if I have the cruise control on and start encountering hills. I am towing a 2000 Jeep Grand Cherokee 4X2 with Remco drive shaft disconnect and have plenty of power since the Chieftain is much lighter than most of the newer coaches. Good Luck.

EasyDoesIt · 07-27-2008, 10:34 AM

I don't think my 98 has an economy mode. Appears the mode switch is not used in this year. I have run a test run towing my 95 Deville on a dolly. Other than acceleration I hardly know it's back there. I got 10.5 mpg running mostly 55mph on a 300 mile run.

gmanatl · 07-31-2008, 01:07 PM

Do you have the manuals for your 1998? On my 1999 there is a small bar on the allison transmission box and when I push it a red light comes on in the display indicating economy mode has been engaged. If I push it again the light goes out disengaging the mode. This is explained in my manual and I can tell that the shift points change in the transmission. It shifts quicker in economy mode to get into the upper gears as quickly as possible. Also in economy mode it tries to hold in the upper gears as long as possible before downshifting. In hilly terrain the manual recommends taking it out of economy mode for better performance.