Eco Hubs and 3.07's - in a 2000 M1088 with a 3126 (~24k pounds)

[ckouba]

There is now at least one truck with 3.07 gears and the Eco hubs. Rick came over last yesterday and we spent a LONG quality day together doing a CTIS service in addition to the hub swap. MASSIVE(!!!!) thanks to him for his assistance!

The verdict? I have only driven about 7 miles with it due to the hour we finished but I think it's going to work out just fine. It moves off a stop differently than it did with the reduction drive, but I don't think it's any slower. Acceleration was a bit "softer" at some points in the gear/rev range, but the interesting thing is it appears to pull the mild hills better than with the reduction gears. I was able to maintain ~60 MPH up a hill where previously it would drop down gears and spin the motor while dropping into the low 50's.

I am back to work for a few days so I don't have time to do a fuel burn run, but I can tell you that my anxiety over "will this work" is gone. I know this might not be everyone's cup of tea, but I can tell you for my build's mission statement, this mod feels great.

More impressions will be shared as we log more miles.

 

[Ronmar]

Can you list your engine model/HP and the total weight of your vehicle?

 

[GeneralDisorder]

His truck is a 2000 M1088 with the 330/860 3126b I believe he is tipping the scales around 24k lbs with his habitat.

Test drive felt really good. Very smooth shifts and didn't lack for power that I could tell anyway. Took about 12.5 hours but that was with an hour break for lunch and to wash the grease from the inner bearings at my shop.

 

[NDT]

I believe the reason these hubs are working out so well is that previously the Cat spent all its time at redline against the governor whereas the torque peak is half that.

 

[Keith Knight]

I would love to hear the fuel mileage. Something else I am curious about is slow speed rock crawling ability. I seen the videos posted recently and it seems as though you really have to get the rpm’s up when you’re up against an obstacle before it can build torque and over come it. Not the most ideal for slow trail traversing.

 

[GeneralDisorder]

I would love to hear the fuel mileage. Something else I am curious about is slow speed rock crawling ability. I seen the videos posted recently and it seems as though you really have to get the rpm’s up when you’re up against an obstacle before it can build torque and over come it. Not the most ideal for slow trail traversing.

The videos you saw were all done in 2nd gear. 1st is much slower.

 

[ckouba]

Rick is close on the truck specs- 2000 M1088 with 3126 and 330 horse tune, with a current weight of ~24k.

He is spot on with the results though, it felt exactly as I thought/expected it would- which is to say not really different performance, just a different engine note. I am extremely happy with it.

 

[ckouba]

Put truck details in thread title too.

 

[Ronmar]

Thanks!
I think the transmission is happier being more heavilly loaded. I suspect the pulse width control programming was never quite right or even optimized for the 7.8:1 axle ratio. Since I started playing with one of these and its hard shifting(mine is a cab and chassis at ~14K), I have speculated that perhaps the programming and adaptability to learn is at the end of its range. Basically as soon as it starts modulating the oncoming clutch, it starts out with enough pressure to provide enough friction to lockup nearly immediately at the load applied. Loading it up brings it more into its ability to smoothly engage the clutch.

i don’t think having to ramp up the RPM and torque a bit at slow speeds is going to be an issue. With it originally being able to move the vehicle right off/near idle, you have to use the brakes to override the engine As you can only go so low on engine output. By moving more into the TCs midrange, and letting it match engine to load, you may be able to more easily control movement only using the throttle, as you now have somewhere to go BELOW the amount of torque needed to move the vehicle…

 

[Keith Knight]

Interesting way to think about it. I’m seriously watching this hoping it’s the cat’s meow and would love to do this, this winter and increase my mileage. I forget has anyone posted a MPG with this modification?

 

[GeneralDisorder]

Interesting way to think about it. I’m seriously watching this hoping it’s the cat’s meow and would love to do this, this winter and increase my mileage. I forget has anyone posted a MPG with this modification?

Yes. My 1079 clocked 10.19 mpg over 118 miles with cruise control set to 55 mph.

 

[Keith Knight]

That’s amazing, what is your vehicle specs, weight year, HP,

 

[GeneralDisorder]

That’s amazing, what is your vehicle specs, weight year, HP,

My truck is a 2008 M1079A1R, C7 @ 370 HP / 931 TQ, stock 3.90:1 R&P's, 21k lbs.

 

[Keith Knight]

So mine is a 2003 1078 converted to a 1079 with a 3126B reprogrammed by caterpillar to 330 HP and the high speed gears installed and fully loaded 28,000 lbs. Curious what I might expect?

 

[Xengineguy]

Interesting way to think about it. I’m seriously watching this hoping it’s the cat’s meow and would love to do this, this winter and increase my mileage. I forget has anyone posted a MPG with this modification?

In one of my earlier posts I did a simple fuel mileage run and reported 11.03 mpg. 50 miles each way 60/65 mph
2001 m1078 3126 274 hp stock. I know it’s hard to believe but that’s what it got.

 

[Third From Texas]

Yes. My 1079 clocked 10.19 mpg over 118 miles with cruise control set to 55 mph.

What was the mpg prior to the ECO's?

 

[Lostchain]

I would love to hear the fuel mileage. Something else I am curious about is slow speed rock crawling ability. I seen the videos posted recently and it seems as though you really have to get the rpm’s up when you’re up against an obstacle before it can build torque and over come it. Not the most ideal for slow trail traversing.

I’m not sure this would be considered rock crawling, but I took a video climbing up what we are thinking was a 30 degree trail. I left it in 1st and it climbed like a champ absolutely no concerns at all. I bet it would have climbed it in 2nd no prob, but 1st was pretty nice, I could wind it out pretty good, and it had great authority on the hill. Check out the vid below the pic.

IMG_3983.mov

drive.google.com

 

[Ronmar]

Sounds like you exceeded peak torque RPM, so you had torque to spare. The real test would be to stop on the hill then start again, noting the engine RPM at which it just starts to move again. I have a 3116 so that is where my math is mostly based around. I have not been able to find an idle/engagement torque spec for the 3116. Engagement torque is used to determine manual transmission ratios, as it is the maximum torque available at idle RPM to pass thru a clutch to get a particular load started. I am guestimating that the 3116 engagement torque is around 200ft/lb. Between 750 and 1450, that 200ft/lb increases in a fairly straight curve to 620ft/lb.

I am calculating that a 3116(225HP@620ft/lb pk torque) should be able to deliver, with 3.9 diffs, ~13,200 pounds of thrust/pull at peak torque in 1st gear. A slope calculator says it should be able to pull 20,000#(my target all-up weight) up a 41.3 degree slope. Since there are some spec numbers published here, give me a bit and I will crunch out some other theoretical limits this evening.

Anyone have the peak torque spec for the 3126 stock 274HP tune handy?

 

[Keith Knight]

Video looks great but I’m with Ronmar, like many times while traversing very technical terrain you can’t just fly up it. Most of the time you are controlling the speed just barely enough momentum to get over the obstacles without throwing everyone and everything all over the place. Inevitably we miss calculate and don’t overcome the obstacle and have to hit the brake let everything settle down and not roll backwards then hit it again with a little more throttle to get over it. I’ve never been a fan of the rock bouncers!

 

[Ronmar]

Keith, that wasn’t really the point I was trying to make, he could have gone a lot slower, even down to a crawl, because it appears he had the torque he needed to do so on that slope. Like in sand and snow, a little momentum can help carry you across fluctuating traction, but it doesn't last long…

I took some of the torque figures listed here and crunched some numbers. Now of course traction and a myriad of other variables like if they chose the TC stall to correctly coincide with PK torque not withstanding, here are some rough capability calculations:

Of course my 3116, 225@620FT/LB. At peak torque/TC stall and 3.9:1, should deliver 13,200lb of force, It should be able to drag 20K up a 41.3deg slope.
DS Torque 3652FT/LB. 60%

Stock 3126, 274@~800FT/LB. With 3.9:1 at peak torque/TC stall should deliver 17,035lb of thrust. It should be able to drag 24K up 45.2 degrees.
DS Torque 4712FT/LB. 78%

Ckoubas Tweaked 3126, 330@860FT/LB. @3.07:1 and peak torque, you should have 14,414lb of thrust, or enough to drag 24K up a 36.9deg slope.
DS Torque 5066FT/LB. 84%

And Generals C7, 370@931FT/LB. With 3.9:1 and peak torque, thats a whopping 19,823lb of force or enough to drag 21K up a 70deg slope…
DS Torque 5484FT/LB. 91.4%

Found my old notes on driveshafts, anyone know what wall thickness tube ours uses?

Based on 279 U-joints we use type 16 driveshafts(Rockwell/Meritor 16R, Dana-Spicer 1610?) with 4” tubes, they make weld yolks for .109 and .134 wall thickness. The two different thickness shafts are rated at 6000 and 6500FT/LB max torque(peak) respectively. The U-joints have a rated yield of 7100FT/LB.

The percentages I listed above are %load related to the 6K shaft rating…

YMMV…