Upshifting 6 speed Allison

[danes-on-tour]

We have a Cummins ISL 400HP and a 6 speed Allison transmission.

MH goes into 6th gear at 58MPH. Travelling on flat ground it will remain in 6th gear all the way below 50MPH unless we try to accelerate.

What we would like to be able to do, but can't, is at say 55MPH - flat ground - no significant engine boost, to manually take it into 6th gear without accelerating up to or over 58MPH.

Why?

Because when travelling on smaller roads without too much traffic, and where the speed limit is 55MPH, we set the cruise control at 55MPH. Then we hit an hill, and the transmission shifts to 5th gear. Once over the hill we then have to push past the speed limit to get back to 6th gear.

Small problem? We agree, but it would be nice if there was a way to upshift manually. We do realize that we could have Allison reprogram the transmission so that it shifts to 6th at 55MPH, but we doubt if the cost will warrant the inconvenience.

Any thoughts?

[topdownman]

I find this interesting, and have noticed much the same with my Allison.

[stephen44]

Originally Posted by The Danes Are Coming

We have a Cummins ISL 400HP and a 6 speed Allison transmission.

MH goes into 6th gear at 58MPH. Travelling on flat ground it will remain in 6th gear all the way below 50MPH unless we try to accelerate.

What we would like to be able to do, but can't, is at say 55MPH - flat ground - no significant engine boost, to manually take it into 6th gear without accelerating up to or over 58MPH.

Why?

Because when travelling on smaller roads without too much traffic, and where the speed limit is 55MPH, we set the cruise control at 55MPH. Then we hit an hill, and the transmission shifts to 5th gear. Once over the hill we then have to push past the speed limit to get back to 6th gear.

Small problem? We agree, but it would be nice if there was a way to upshift manually. We do realize that we could have Allison reprogram the transmission so that it shifts to 6th at 55MPH, but we doubt if the cost will warrant the inconvenience.

Any thoughts?

does altering the mode to economy (if you have this option) not make it shift sooner ?

Stephen
1999 Tradition

[danes-on-tour]

Originally Posted by stephen44

does altering the mode to economy (if you have this option) not make it shift sooner ?

Stephen
1999 Tradition

Hi Stephen

I forgot to mention - the behavior that I describe is in economy mode. This is of course relevant.

[RickO]

We have the same drive train and I've noticed the same thing.

Have you tried using the economy mode? At any rate, I would think a call to an Allison/Cummins shop would be in order. I'm thinking the cost would be "minimal".

Rick

[Gary RVRoamer]

The problem is the engine rpms and available torque. 55 mph in 6th gear puts you below the sweet spot for economy and driveability that has been calculated for your engine and gearing combination. However, that spot was calculated for a range of weights and conditions and maybe your particular coach could indeed do fine at 55 mph in 6th.

Minimal cost for reprogramming at an Allison shop s probably something like $300. That's just a guess, but their bill or estimate never seems to come out any less. I think i would just set the cruise for 58 instead of 55!

[dons2346]

Originally Posted by Gary RVRoamer

The problem is the engine rpms and available torque. 55 mph in 6th gear puts you below the sweet spot for economy and driveability that has been calculated for your engine and gearing combination. However, that spot was calculated for a range of weights and conditions and maybe your particular coach could indeed do fine at 55 mph in 6th.

Minimal cost for reprogramming at an Allison shop s probably something like $300. That's just a guess, but their bill or estimate never seems to come out any less. I think i would just set the cruise for 58 instead of 55!

I would suggest the 58-60 MPH figure also, I found that my MPG went up even at the faster speed.

[Doug Sage]

My Suncruiser has the 6 speed Alison. I have a switch on the dash called Overdrive. It will lock the transmission out of 6th gear or 5th and 6th gear. I can just rock it down a notch and do exactly what you are asking about. I don't know if this switch exists on diesel motorhomes.

[Mr_D]

Originally Posted by Doug Sage

My Suncruiser has the 6 speed Alison. I have a switch on the dash called Overdrive. It will lock the transmission out of 6th gear or 5th and 6th gear. I can just rock it down a notch and do exactly what you are asking about. I don't know if this switch exists on diesel motorhomes.

Nope.

[YC1]

Check around page 55 for the adaptive transmission procedure. You can re-train the tranny yourself.

The econ mode on off definitely will change the shift schedule on mine.

[Happycarz]

Henrik,
Mine is the same, with the exception of a 60 MPH gear 6 shift point. All the other upshifts are altered when in economy mode. Why not 6th? I have the Aladdin Jr. and it will stay in 5th at 59.5 MPH. I have to obtain 60 MPH or it won't upshift. Once in 6th I can maintain 6th down into the low 50's, now with the MP-8. Before the MP-8, it would downshift to 5th with only the slightest throttle pressure.

My local Allison wants me to pay for them to get the necessary software and then 1 hour labor, somewhere around $375? Not! I think I'll mail my TCM to the Allison dealer in Coburg, OR to reprogram a 57 MPH 5-6 shift into mine. Should be $200.

[ru499]

Both 5th & 6th gears are overdrive. The rpm difference is very small between the 2. I wouldn't worry about it running in 5th at 55 mph.Running your engine at low rpm's is not good for it. The computer wants it in 5th because that's where the rpm should be.

[WILDEBILL308]

I was having a similar problem with mine but didn’t know it wasn’t up shifting till late in the trip. I got 8.5 mpg towing my Honda on a tow dolly and running most of the time in 5th. The point is you may not get better mileage forcing your coach to up shift before it is designed to.
Bill

[MoonchaserTX]

Coming home from a recent trip I was easing off the pedal when climbing hills (we do live in Hill Country Texas!) so as to stay in 6'th down to 50 or so (as an experiment for fuel savings) and the [PDF]HEST (High Exhaust System Temperature) yellow dash light came on...it went off after driving 20 miles or so, but after checking it out when I got home, I was told by multiple people that "dogging it" down in RPM not only will not increase mileage but makes the engine work too hard below it's power range and thus the exhaust gets hot (the engine temp gauge stayed right at the normal 200 degrees or so).

Any comments on what I was told?

Thanks!