ECO Hubs Who needs 3:07 gears?

[Ronmar]

Ok, on that tune you are probably going to ramp pretty steadily from ~300ft/lb at idle to ~800 ft/lb at 1450RPM. Thats ~72 ft/lb of increase per 100 RPM. If you advance the pedal slowly and note at what engine RPM the truck starts to move, we can get an idea how much engine torque it is taking to pull your truck up that 10%/5.7deg slope. And of course how accurate is that 10% slope number Details details...

 

[MatthewWBailey]

Ok, on that tune you are probably going to ramp pretty steadily from ~300ft/lb at idle to ~800 ft/lb at 1450RPM. Thats ~72 ft/lb of increase per 100 RPM. If you advance the pedal slowly and note at what engine RPM the truck starts to move, we can get an idea how much engine torque it is taking to pull your truck up that 10%/5.7deg slope. And of course how accurate is that 10% slope number Details details...

I'll go measure it. I have a 12' level

 

[MatthewWBailey]

I'll go measure it. I have a 12' level

And of course how accurate is that 10% slope number Details details...

Here's the measurement. It's only a 40' section of driveway but rises at 9.75 degrees. I was surprised it was that much. No wonder I spin around when plowing snow. The backhoe does a 180 on that spot without my chains. So that comes to 17% grade.
It's a pain bc I have to stop dead on that rise for traffic to pass.

 

[Ronmar]

Ok, so nearly 10deg not 10%… be curious what engine RPM it takes to get you moving on that slope…

 

[MatthewWBailey]

Ok, so nearly 10deg not 10%… be curious what engine RPM it takes to get you moving on that slope…

I'm rigging up my tach off the alt R terminal just to test it. I can use the spare/unused 568A energize wire from K11 since it's already up in the PDP. The delco instructions say 10pulses per rpm, then I got the pulley ratio too. I think that's 2.5:1

 

[ckouba]

Mileage update: ~25k pounds, 6x6, 3.09's, Goodyear MVT's, big box on back (12' 4" high, 8' wide), kept speed at or below (most of the time) 65 mph

Portland, OR to Henderson Utah; 887 miles, 108.9 gal gives 8.13 mpg.

No issues with drivability.

 

[Ronmar]

I came across someone who had a driveshaft failure(non eco hub LMTV) that split the tube. He was able to measure the tube thickness and he came up with .134” wall thickness. That is the heavier of the two specced wall thicknesses, found on the #6500 peak torque version…

 

[Ronmar]

Tach goes in on Tuesday lol. Weight was 17400 at the last scale i was on. Rpm sounded like the same level as the high idle but it's just a swag.

A 17,400# truck should require 3,021# of thrust to crawl up a 10* slope. With the 70/30 torque split in 2nd gear, thats,~453# for each front tire and 1057# for each rear tire. So 1057# times 1.942’ tire radius = 2053ft/lb on each rear axle, so 4106 total out of the rear diff, divided by a 3.07 diff = ~1370ft/lb from the rear driveshaft to produce that much tire thrust and about 647ft/lb from the front DS. Thats ~2015ft/lb total from the transmission to make ~3000# of thrust. With a 4.18 total ratio in 2nd gear and considering gearbox losses, thats ~540ft/lb out of the torque converter into the coupled 2nd gear ratio.

Here is where the math gets a little muddier… Low-mid range torque converter multiplication is a little more difficult to estimate as the multiplication increases with the difference between input RPM and turbine/output RPM. And of course the magic of the TC is it will match output to load. The 275hp 3126 tune will deliver from ~400-800 ft/lb between 800 and 1450 RPM? and the torque it delivers will mix with that variable torque multiplication until it reaches stall or the turbine output shaft starts to rotate. But since the required torque of ~540 ft/lb falls in your available range of 0-~1600 ft/lb it obviously moves. If we know the RPM it takes to start moving on that 10* slope, we can estimate engine produced torque, and then estimate converter multiplication at that RPM difference when the truck just first starts to move. In the end it should only take about 1/3 of what you are capable of delivering into the gearbox…

You want to advance the pedal slowly, as it is a speed selector not a throttle. The pedal tells the governor or ECU what RPM to run at, and it in turn delivers fuel as it is “programmed” to achieve that commanded RPM… if it sees a big difference between actual and commanded RPM, it will throw a lot of fuel at it making it difficult to capture the RPM when it first starts to move on the slope… ideally you would want to have someone chock the wheels so you could start from setting against the chocks to take any possible brake resistance out of the picture. You should also be able to hover using the pedal to vary RPM, at a particular spot uphill from the the chocks or once your foot is off the brake after you start normally…

 

[MatthewWBailey]

A 17,400# truck should require 3,021# of thrust to crawl up a 10* slope. With the 70/30 torque split in 2nd gear, thats,~453# for each front tire and 1057# for each rear tire. So 1057# times 1.942’ tire radius = 2053ft/lb on each rear axle, so 4106 total out of the rear diff, divided by a 3.07 diff = ~1370ft/lb from the rear driveshaft to produce that much tire thrust and about 647ft/lb from the front DS. Thats ~2015ft/lb total from the transmission to make ~3000# of thrust. With a 4.18 total ratio in 2nd gear and considering gearbox losses, thats ~540ft/lb out of the torque converter into the coupled 2nd gear ratio.

Here is where the math gets a little muddier… Low-mid range torque converter multiplication is a little more difficult to estimate as the multiplication increases with the difference between input RPM and turbine/output RPM. And of course the magic of the TC is it will match output to load. The 275hp 3126 tune will deliver from ~400-800 ft/lb between 800 and 1450 RPM? and the torque it delivers will mix with that variable torque multiplication until it reaches stall or the turbine output shaft starts to rotate. But since the required torque of ~540 ft/lb falls in your available range of 0-~1600 ft/lb it obviously moves. If we know the RPM it takes to start moving on that 10* slope, we can estimate engine produced torque, and then estimate converter multiplication at that RPM difference when the truck just first starts to move. In the end it should only take about 1/3 of what you are capable of delivering into the gearbox…

You want to advance the pedal slowly, as it is a speed selector not a throttle. The pedal tells the governor or ECU what RPM to run at, and it in turn delivers fuel as it is “programmed” to achieve that commanded RPM… if it sees a big difference between actual and commanded RPM, it will throw a lot of fuel at it making it difficult to capture the RPM when it first starts to move on the slope…

It barely starts moving at 1200rpm from a dead stop on the slope. I was barely on the throttle. It kept moving steadily, barely, until I got to the top and then started accel.

With the tach in there, it's easy to see your point in the last paragraph. I was driving up the hill back to the house which is a steady 6% grade at 44mph and 1600rpm. I just tried to hold 1600 and I could hear the engine getting louder as the slope increased to 7% on the last section bf my house.

if I hold pedal steady on flats, it's shifting at 1850.

also interesting from your calcs that "thrust" to get moving is almost exactly the vertical lift component of the weight at 17.3%, grade is 17.18%. Neat

 

[MatthewWBailey]

You should also be able to hover using the pedal to vary RPM

It was holding at 1100rpm. I came off the brake and let it sit for a second at 1100. Had to get to 1200 to start creeping. But it did start accelerating at 1200 albeit slowly. So maybe 1150 is the threshold

 

[Gunny 0369]

Mileage update: ~25k pounds, 6x6, 3.09's, Goodyear MVT's, big box on back (12' 4" high, 8' wide), kept speed at or below (most of the time) 65 mph

Portland, OR to Henderson Utah; 887 miles, 108.9 gal gives 8.13 mpg.

No issues with drivability.

more of this.

ckouba, what terrain were you on, and did you climb any mountain passes?

Im about the same size as you, no ECO, averaging 7.2 mpg - best 7.7 worst 4.8 (headwind) 5500 miles NC to MT, Canada and back) passes are slow, down to 35-40 on the climb up the 9600 footers.
3116 ATTAC mechanical A0.

 

[ckouba]

more of this.

ckouba, what terrain were you on, and did you climb any mountain passes?

Im about the same size as you, no ECO, averaging 7.2 mpg - best 7.7 worst 4.8 (headwind) 5500 miles NC to MT, Canada and back) passes are slow, down to 35-40 on the climb up the 9600 footers.
3116 ATTAC mechanical A0.

Still out on the trip but can drop a note...

Check out the elevation profile of I-84 from Portland to SLC, then I-15 to Spanish Fork, then Rt 6 over to Price. Winds were pretty calm, for the most part. We had a bit of a storm into SLC but nothing outrageous. That leg was a best of 8.8, worst of 8.2, keeping it (mostly) under 65. We've been on a reasonably even mix of dirt and pave since then and still pulling in the 7's.

We haven't been too high, but have spent a bit of time over 7k so far this trip. Currently around 6k as I write this. Freeway pass work can drop me into the 40's (Emmigrant Hill east of Pendleton as an example, or Soldier Pass on Rt 6 to almost 9k), but it's comparable to the other big rigs out there, and I always seem to be a little bit faster than them. I don't try to make up any time heading up hill either...

Full pavement tanks seem to be in the 8.5 mpg range, as long as I control my speed. It just wants to run on the flat and open.

 

[MatthewWBailey]

Give me a post #, and I will do that.

I went thru it, and all the posts from #590 ... to #625, EXCEPT 613 are all part of the Allison Stall test discussion.
New thread I started is called "LMTV Allison Stall Test issues"

 

[ckouba]

more of this.

ckouba, what terrain were you on, and did you climb any mountain passes?

Im about the same size as you, no ECO, averaging 7.2 mpg - best 7.7 worst 4.8 (headwind) 5500 miles NC to MT, Canada and back) passes are slow, down to 35-40 on the climb up the 9600 footers.
3116 ATTAC mechanical A0.

Gunny,

Despite a number of other people discussing their rig configurations and mileage impacts, my prior reply to you was deleted because "The folks who have been posting in the Thread 'ECO Hubs who needs 3:07 Gears?' have requested that you start your own thread about your current trip."

Not sure I understand why my mileage data and user experience from the hub delete isn't relevant to this conversation. It's a 2000 M1088, ~26k #, 8' wide, 12' 5" high, ~23' box on back, 3.07's with the Eco Hubs, 330hp 3126.

I will share again that I was on I-84 and I-15 from Portland to Spanish Fork, and then Rt 6 over to Wellington (9k Soldier Pass). For this leg I averaged about 8.5 MPG fully loaded and keeping it under 65 (or trying). Uphill travel I was sympathetic and slowed, but was never as slow as the big rigs. Once I hit the dirt, mileage dropped into the low 7's typically, with some smaller fills of high 6's. I had one outlier of ~55 miles on ~10.5 gallons, but that was on a bunch of uphill, rough dirt/gravel road at higher altitude (up to 7,900'). Our return route was the same from Spanish Fork back to Portland, and I still need to fill up following our last leg to home, but if I had to guess, I'd say we averaged just over 8 MPG for the entire trip, with a high of 8.9 MPG on two highway tanks.

One destination later in the trip, I had an extremely sandy stretch for about an hour each way. The truck was lighter than the start, but not by much (just food and water depletion), and it was able to dispense with the terrain without issue. This was also a ~5 MPG fill as well. There was a 0.3 mile stretch where the soft, loose sand was as deep as the sidewalls. My wife caught our departure on video:

You can see the sand billowing away from the tires. It was extremely soft and fairly deep. Truck did fine without the reduction set.

I am happy to support Mike and share any other info about my personal experience with the Eco Hubs. They are well made and have been a great mod for my application. If I were still considering them, this is exactly the info I'd be looking for. Ask away with any other question or send me a PM if you'd prefer.

Mods - Respectfully, if this is still considered inappropriate, please let me know what I need to filter out to share the experience instead of deleting it.

Chris

 

[Guyfang]

I most humbly apologize. I misunderstood someone else about the thread getting off topic and soft deleted your posts. So here they all are "reanimated". Again, sorry.

 

[ckouba]

I most humbly apologize. I misunderstood someone else about the thread getting off topic and soft deleted your posts. So here they all are "reanimated". Again, sorry.

No worries at all. I assume that volunteers keep the forum running and I appreciate the efforts, even if everything doesn't go perfectly. Fact is, I wouldn't be doing this without the support of this forum, so I contribute what I can as content and happily $'s support it as well. I didn't want to make a stink over it, but I also legitimately thought the info was useful. Thanks for reviving it.

 

[Gunny 0369]

Gunny,

Despite a number of other people discussing their rig configurations and mileage impacts, my prior reply to you was deleted because "The folks who have been posting in the Thread 'ECO Hubs who needs 3:07 Gears?' have requested that you start your own thread about your current trip."

Not sure I understand why my mileage data and user experience from the hub delete isn't relevant to this conversation. It's a 2000 M1088, ~26k #, 8' wide, 12' 5" high, ~23' box on back, 3.07's with the Eco Hubs, 330hp 3126.

I will share again that I was on I-84 and I-15 from Portland to Spanish Fork, and then Rt 6 over to Wellington (9k Soldier Pass). For this leg I averaged about 8.5 MPG fully loaded and keeping it under 65 (or trying). Uphill travel I was sympathetic and slowed, but was never as slow as the big rigs. Once I hit the dirt, mileage dropped into the low 7's typically, with some smaller fills of high 6's. I had one outlier of ~55 miles on ~10.5 gallons, but that was on a bunch of uphill, rough dirt/gravel road at higher altitude (up to 7,900'). Our return route was the same from Spanish Fork back to Portland, and I still need to fill up following our last leg to home, but if I had to guess, I'd say we averaged just over 8 MPG for the entire trip, with a high of 8.9 MPG on two highway tanks.

One destination later in the trip, I had an extremely sandy stretch for about an hour each way. The truck was lighter than the start, but not by much (just food and water depletion), and it was able to dispense with the terrain without issue. This was also a ~5 MPG fill as well. There was a 0.3 mile stretch where the soft, loose sand was as deep as the sidewalls. My wife caught our departure on video:

You can see the sand billowing away from the tires. It was extremely soft and fairly deep. Truck did fine without the reduction set.

I am happy to support Mike and share any other info about my personal experience with the Eco Hubs. They are well made and have been a great mod for my application. If I were still considering them, this is exactly the info I'd be looking for. Ask away with any other question or send me a PM if you'd prefer.

Mods - Respectfully, if this is still considered inappropriate, please let me know what I need to filter out to share the experience instead of deleting it.

Chris

perfect info.
This will help others quite a bit
Thank you!

 

[MatthewWBailey]

So back on topic, since it was me that got us off topic: I was wondering what the forum feedback is on me staying with the 3.07 gears AND Eco hubs instead of swapping back to 3.90? I'm still putting in 2 of the Detroit lockers (meritor version) so I'll be pulling the diffs regardless, but curious on the benefits of the 3.90 gearing before I install the lockers. I have a set of 3.90 axles already. The only 'lessor' functional 'thing' with this 3.07 combo is that I never see 7th gear. And The shifting interaction between 6th and 5th on lite rolling highway hills can be frequent unless I hold it to 5 on the wtec. That's probably road dependent anyway. Once I do the 330hp flash, that may go away. Thoughts?

 

[GeneralDisorder]

3.90's will be better. But 3.07's can work if you aren't crazy heavy. The ideal ratio would be somewhere around 4.5 but AFAIK there's no one making R&P sets in alternate ratios. 3.07's are what @ckouba is running and he's probably as heavy as I would recommend with that gearing and power - around 25k lbs or less.

If you can swap to 3.90's then I would recommend it. If you can't and you stay light you'll be fine.

 

[Ronmar]

What general said, 3.9 is closer to ideal, but if you watch your weight...