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Ditto
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FMTV Highway Speed
- Thread starter NDT
- Start date
- 1,998
- 5,126
- 113
- Location
- Portland, OR
With 370 HP and 931 Ft/lbs my truck gear limits at 62 mph - and it gets there in a hurry! You hit the engine and transmission red line and that's all it's got - mathematically impossible to exceed with the engine and transmission programming and probably not smart to exceed the engine red line anyway. I'm sure with high speed gears I could max those out also.
coachgeo
Well-known member
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****NOT GOOD IDEA for full time use ... mayyyyyyyybe if it is nothing more than a Parade Queen.
Reason being is easy to understand. Look under trucks with no outer gear reduction or Portal design..... notice the size of their pumpkin... hint:- they are much larger pumpkins etc. compared to axles that have some geari-ish gizmo on the ends like our trucks. They are larger cause they need thick beefy parts inside the pumpkin* because the gears in the pumpkin takes most ALL the forces.
On rigs with some geari-ish gizmo on the ends.... the forces get shared you could say 50/50 between the parts in the pumpkin and those geari-ish gizmo's... thus allowing the parts inside the pumpkin to be 50% less beefy, and smaller pumpkin needed to fit those parts in.
Take away the geari-ish gizmo by going 1:1 and now your pumpkin inner parts intended to take 50% of the forces are taking 100% of the forces.!!! Thus you will break things!!!
UPDATE: 4/17/24 CHANGED MY MIND. totally forgot to consider that the eco hub ... while their install does pull out OEM parts....... it also puts different parts in their place.... so there is actually not a loss of of big steel parts in the hub to share forces with like I was at first thinking (or not thinking .... matters how you look at it LOL) ..
*yeah for simplicity; I skipped that the forces are also shared with Axle shafts... those too are usually beefier if there is no geari-ish gizmo on the ends.
****that is If understand this right.... If not, someone one will kindly correct my points..... or tarnish me to depths of hell for posting... lol.. don't really care... either one will help all of us to learn from the mistake(s).
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TacMac2012
Active member
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- Wallburg, NC
I am not factoring strength into the mix at all. I am just saying changing the hubs to 1:1 is stupid because of the gear ratio. It would DOUBLE the speed in every year, which would likely burn out the transmission in a hurry. Plus, why does anyone need an LMTV that will run 116?
It's a great idea with a different ratio maybe, such as 1.5:1 or whatever.
coachgeo
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Apologize.. quoted your post by mistake. Meant to be another's post quoted. Fixed it up above now.
I'd suggest us two delete our post to help clean up the thread of unnecessary content.... but that option is unusually not available on this board to members (mods/admins can though) . If you just erase the content and replace it with "MOD- please delete this post"... then I'll do the same with this one.... or just leave it.... matters not to me.
BigMontana
Member
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- Polson, MT
The people you hear about constantly blowing drivelines and transmissions are the same people who need to go faster than 55.
I run mine at 47 all day long on the highways and byways with the farmers. On most two lane country highways 45 MPH and below is the speed at which you need to legally turn on flashers.
They made this thing as cheap as possible to meet the minimum required contract standards, start trying to exceed design speed...bad things happen.
Chill out and be on vacation when you are on vacation and it'll last a good long time.
Rev. Dr. Deke
- 1,998
- 5,126
- 113
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- Portland, OR
That post from before the ECO hubs were introduced was mistaken in their understanding of the 1:1 reduction hubs delete. It doesn't double the drivetrain speeds, it cuts them in half. Makes everything turn slower.
And the ring/pinion size is only 1/10" smaller in diameter than other similar load rated axles from Dana, etc. With the 3.90 gear ratio the teeth are very large and chunky as well so the R&P is plenty strong enough for 1:1.
With the increase in power of the 370/931 map and the ECO hubs my truck accelerates faster in every condition, up grades, etc. And I cruise at 75-80 mph with a nice quiet cab. It's a totally different truck. No desire to go back whatsoever.
And the ring/pinion size is only 1/10" smaller in diameter than other similar load rated axles from Dana, etc. With the 3.90 gear ratio the teeth are very large and chunky as well so the R&P is plenty strong enough for 1:1.
With the increase in power of the 370/931 map and the ECO hubs my truck accelerates faster in every condition, up grades, etc. And I cruise at 75-80 mph with a nice quiet cab. It's a totally different truck. No desire to go back whatsoever.
coachgeo
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- North of Cincy OH
NOPE... folk threw drive lines below 55 (w/out eco hubs)
- 794
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- Mesa Colorado
All my highways are 75 here. State highways are 55 except thru the sharp river crossings. Can't just arbitrarily drive 47 and claim it's good enough. I'll get pulled over lol. So these so-called highway 3.07 gears are useless, Until Eco mania arrived! Now, Just drove to dinner tonight on a 45mph curvy road. Nice to hear that Cat purring at 1400 rpm the whole way. My wife commented, "what'd you do that we can now have a conversation in the truck?". Seems like a no brainer to me, unless you're hauling lead over tank barriers.
valkrior
New member
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Hey, did you have to have the Allison transmission reprogrammed when you switched to the highway axle gears? I upsized to the 53" tires on my M1081. Now when my speedometer reads 45mph I'm actually running 55mph (in 7th), so it's improved my cruising quite a bit. However, it has a tendency to drop down to 6th when I floor it. I'm wondering if I need to take it to a shop to have the transmission reprogrammed to react to the torque lag differently. Thanks - Jason
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The Allison transmission computer doesn't know or care what your over the road speed is. There is no programming required for gear ratio or tire size changes. The speedo is controlled by the engine computer not the transmission computer.
It's going to downshift when you floor it if you are under the engine's redline in the lower gear. The gear the transmission selects depends ONLY on the engine RPM and throttle position. You have decreased the RPM at any given road speed so now when you floor it the transmission computer sees that it can give you better acceleration by dropping a gear so it does that. This is normal operation. Changing the gear ratio with ECO hubs, 3.07 gears, or (effectively) with tire size will change the shift points in relation to road speed. That's expected.
Ronmar
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The Allison is continually learning and relearning/adapting its shift points. You can force it to drop,all that learned info and relearn them from scratch with a power-on sequence. But it will end up at the same end point eventually. You mashing down the pedal tells the trans controller you want to go faster via the throttle position sensor signal. If it thinks it can do it better by dropping a gear range, it will… There is a programmable input at least on the wtec2&3 for a forced kickdown. That would require TCU programming and a switch to activate…