Would EcoHubs benefit from reprogramming Allison shift points?

[hike]

Here is the link…

Thank you for sharing @Ronmar, this was very interesting.

The two items I most appreciate are: 1— the torque equations versus gear ratios at final; 2— the explanation how they start with matching low gear ratios and work toward lowering rpm's in to the power band at nominal speed.

2— made me wonder if changing the shift points with the 3.90 rear ends and ecohubs might make sense, especially in 5th, 6th and 7th gears.

I have noticed if we push up into 7th then back off we can cruise hovering 1,200 - 1,400 rpm in the 60's on the interstate while holding 7th gear. I suspect this would result in a favorable mpg range while traveling interstates across middle America. I would prefer not exceeding our tire's maximum speed to find 7th gear—

 

[Keith Knight]

It would have to benefit from reprogramming and getting 7th gear back in use. What speed are you able to get 7th gear to engage? I’m in a 2003, with 3.90 and eco hubs. Hit 80 tried to get it to shift into 7th and it wouldn’t so I gave up. My normal top speed is 60 and never want to go 80 again.

 

[hike]

It would have to benefit from reprogramming and getting 7th gear back in use. What speed are you able to get 7th gear to engage? I’m in a 2003, with 3.90 and eco hubs. Hit 80 tried to get it to shift into 7th and it wouldn’t so I gave up. My normal top speed is 60 and never want to go 80 again.

We also have a 2003 M1078A1 (330hp tune) with EcoHubs

We shift into 7th below 80 on our Bluetooth speedometer, below 75 on the dash speedometer. We like to sit in the 60-65 range (haven't added cruise control yet). At 62 in 7th we are at 1,200 rpm, 62 in 6th 1,500. She won't hold 7th at 60 now, and that may be too low. I think ronmar said a year or so ago that EcoHubs with 4.50 rear end would be about perfect. That's about 230 rpm lower.

With the EcoHubs if the up shift points were maybe 200 rpm lower it would make 7th more obtainable, though perhaps that would also put us under the power band too often?

 

[hike]

I'll also note in the video @Ronmar shared the Allison boys commented that the medium sized engines didn't need the 7 speed. And I think all of us with EcoHubs have shown that is true—

 

[Keith Knight]

I’m loving the 8.5-9 mpg.
It would be very difficult to change the program it would be easier if we could find a program already in use by a different vehicle with the same engine and transmission. Probably like finding a unicorn.

 

[GeneralDisorder]

Mine gets to 7th just above 70 mph, and stays in 7th down into the lower 60's. I'll try to shoot a video. I'm setup the same as @Keith Knight but with the C7 and WTEC IV.

IDK but the WTEC IV seems to compensate just fine.

Everyone needs to stop getting wrapped up in the gear number. Realistically the wind resistance at any speed in 7th is going to more than delete any fuel savings from the very slight reduction in RPM. 60 MPH is already faster than optimal and is a very happy speed for me and my truck and optimal RPM for that speed is 6th gear. 7th will have the engine turning too slow and under that heavy load you need RPM to keep up the oil pressure and hydrodynamic film strength. Engines that are run on the harder side (higher average RPM, higher cylinder pressure) tend to last longer - they have higher cylinder pressure which keeps rings seated and prevents blow-by fouling the oil, and the higher RPM (faster sliding speed between parts) moves you up the Stribeck curve:

Stribeck curve - Wikipedia

en.wikipedia.org

Moving up the curve = good for engine wear. RPM does that. Staying in a high gear with a very low RPM increases load, and decreases oil pressure and hydrodynamic film. For that reason I would not encourage the Allison to shift earlier or stay in a higher gear longer.

For me it's a non-issue. I've driven plenty of WTEC-III trucks that also had no issues and they don't benefit much from 7th due to their lower power (usually - early A1R being the exception that can take a 370 flash).

 

[hike]

7th will have the engine turning too slow and under that heavy load you need RPM to keep up the oil pressure and hydrodynamic film strength. Engines that are run on the harder side (higher average RPM, higher cylinder pressure) tend to last longer - they have higher cylinder pressure which keeps rings seated and prevents blow-by fouling the oil, and the higher RPM (faster sliding speed between parts) moves you up the Stribeck curve:

Stribeck curve - Wikipedia

en.wikipedia.org

Moving up the curve = good for engine wear. RPM does that. Staying in a high gear with a very low RPM increases load, and decreases oil pressure and hydrodynamic film. For that reason I would not encourage the Allison to shift earlier or stay in a higher gear longer.

This may be related to the Allison comments of needing less gears. Their design encourages lockup as soon as possible to hold almost constant available torque through the gear changes. Keeping the engine in its power band as much as possible.

You answered another of my questions about sitting below the power band for long stretches. I always learn something here—

 

[Ronmar]

I think shift point programming will be an Allison core programming thing and not accessible by any of us mere mortals…

Allison Routinely locks out the second OD(our 7th gear) in many MD3060(our core transmission) applications. This is a common topic on the schoolie conversion forums, "how do I get my 6th gear back) it typically has to be authorized by Allison... Based on how it performs with 3.9 final, I suspect Allison engineering would have done the same on this vehicle if it had been presented with 3.9 final gearing vis 7.8 in this deal with the manufacturer...

The 3116 having a peak torque a few hundred RPM higher than the 3126/C7, 6th actually is a good match IMO

 

[fuzzytoaster]

What you could try is getting an iScaan done which is "old school" for them. Most dealers don't know about it but Allison can take all your vehicle's info and put it into their machine and get a custom shift program. That being said.. don't get your hopes high on the word "custom" as they will tailor it as they see fit within parameters based on your request. You can't change one gear to engage lower/higher/etc, it has to be all gears being modified. They want "smooth shift" more than anything and will fight you to the point they will decline to help if you push too hard.

This is coming from experience when unlocking 6th gear in my M915A4R2 with the Allison 4500SP double OD. They didn't even have an iScaan for my truck model so going through the steps and getting authorization from them to proceed officially was a task in it self. The senior corporate advisor based out of Kansas made it seem like Allison was infallible and the way they left the factory was true perfection.. until I showed him 5 military trucks and he never called me back.

 

[GCecchetto]

It would have to benefit from reprogramming and getting 7th gear back in use. What speed are you able to get 7th gear to engage? I’m in a 2003, with 3.90 and eco hubs. Hit 80 tried to get it to shift into 7th and it wouldn’t so I gave up. My normal top speed is 60 and never want to go 80 again.

My C7 powered A1R shifts into 7th at 70mph under normal throttle. If I have my foot in it it’s more like 75. If I run it up to 67 and the slowly lift off the accelerator it will shift into 7th. It will cruise at 60 in 7th as long as it’s pretty flat highway and I keep my foot out of it. I’m running the 370/931 tune, so that likely affects things.

 

[Keith Knight]

My C7 powered A1R shifts into 7th at 70mph under normal throttle. If I have my foot in it it’s more like 75. If I run it up to 67 and the slowly lift off the accelerator it will shift into 7th. It will cruise at 60 in 7th as long as it’s pretty flat highway and I keep my foot out of it. I’m running the 370/931 tune, so that likely affects things.

I tried again yesterday on nice easy down hill 70 then 75 doing as you described still no 7th gear. Oh well. I have the 330 hp tune.

 

[GCecchetto]

I tried again yesterday on nice easy down hill 70 then 75 doing as you described still no 7th gear. Oh well. I have the 330 hp tune.

Hmmm, maybe the earlier trans programs are different?

 

[GeneralDisorder]

Hmmm, maybe the earlier trans programs are different?

The WTEC-II and III were both used by the A0 trucks with the 3116 and the TCM is the same between all WTEC-III trucks so the programming for the II and the III likely has the shift points setup for a lower power/torque engine with less displacement as the HP and torque curves are different between the two applications. Thus the III programming is probably a compromise for the 3126B as it was programmed for the 3116.

The WTEC-IV was and is only paired with the C7. So it's programming is defined by only that engine which is newer, larger, and more powerful at every point along the curve so shifting earlier is possible with more power available to push the higher gearing sooner.

 

[GCecchetto]

The WTEC-II and III were both used by the A0 trucks with the 3116 and the TCM is the same between all WTEC-III trucks so the programming for the II and the III likely has the shift points setup for a lower power/torque engine with less displacement as the HP and torque curves are different between the two applications. Thus the III programming is probably a compromise for the 3126B as it was programmed for the 3116.

The WTEC-IV was and is only paired with the C7. So it's programming is defined by only that engine which is newer, larger, and more powerful at every point along the curve so shifting earlier is possible with more power available to push the higher gearing sooner.

So there you go! We're lucky to have you as a resource GD.