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FMTV High Speed Gears

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isaacnasar

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Eatontown NJ
If you're just looking for the new gears try Joe Boydstun at MTP Drivetrain Services - they are in Many Louisiana and have access to rockwell/meritor parts. I contacted him a few months ago and he can get the gears from Meritor at a cost of $1000 a set. I couldn't find someone in NJ that I felt confident in to do the swap so I abandoned the idea. He did say if I wanted to bring the truck to him it would be billed at 8 hours for the front and 4 hours for the rear for them to do the labor.

It's something I would still love to do but my budget for getting it done is ~$3000 and all other options seem to be more than that.
 
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lesrrt

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Location
Cecil county, MD
I have read this entire thread and find it incredible interesting. So, what is the tally for the gear swap vs mpg increased and top speed potential? Does your mpg increase going 55 vs 65 cruising? I guess 5-6 mpg to 6-10mpg for some would seem ok; does it justify cost and wrench time finally? Just by comparisons and for giggles, what do 5-tons average (mpg) per assume empty flat-road, and cruising speed? Great info Gentleman!!
 
Keith Knight

Keith Knight

Well-known member
Steel Soldiers Supporter
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I have a 2003 M1078A1 with the 3126 CAT. After my gear swap and rear locker install it went from 3.5MPG to 6.5MPG and 69MPH to 73MPH. The MPG was calculated at cruising speed of about 58-60MPH before and after. Using cruise control that I installed and after reconfiguring the CAT ECM/Computer for the new gears so it would show the correct speed.
My goal was to increase Fuel milage and reduce interior noise by lowering the cruising speed RPM and it did both, NOT so I can go Faster!!!
 
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DiverDarrell

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Steel Soldiers Supporter
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Port orchard, WA
It's by far the best upgrade I have done so far. I paid 1.4k for my gears a while ago. Keeps the engine off the red line at 55-60. Made the driving experience much better.
 
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lesrrt

New member
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Location
Cecil county, MD
I wonder if there was a way to disengage the front axle from the permanent AWD drive status. That would seem likely the most drag to be freed; thus making more efficient. I am new and just learning these vehicles. Are the front axles 2:1 ( 1:7) reducers computer controlled? If there was some way to open the front drive up without hindering the safety or original characteristics of what the MV was originally designed for. AWD drive cars and some med duty vehicles have this via the computer. One could take out the front and/or the rear driveshafts to make an experiment. Probably a way to shunt the computer software to allow this. It just would be nice to see if this would render a better result in mpg. I work nights, sorry for the ranting, lol! Some good technicians here, Thanks!!
 
coachgeo

coachgeo

Well-known member
5,120
3,445
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Location
North of Cincy OH
lesrrt said:
I wonder if there was a way to disengage the front axle from the permanent AWD drive status. That would seem likely the most drag to be freed; thus making more efficient. I am new and just learning these vehicles. Are the front axles 2:1 ( 1:7) reducers computer controlled? If there was some way to open the front drive up without hindering the safety or original characteristics of what the MV was originally designed for. AWD drive cars and some med duty vehicles have this via the computer. One could take out the front and/or the rear driveshafts to make an experiment. Probably a way to shunt the computer software to allow this. It just would be nice to see if this would render a better result in mpg. I work nights, sorry for the ranting, lol! Some good technicians here, Thanks!!
Click to expand...
If you remove any drive shaft you will GO nowhere in Highway drive mode. Way the AWD works can be thought of as a differential on an axle. Axle just happens to be sitting north south. Thus when you pull a driveshaft the differential feels that end is slipping and sends all power to it. End result of this is all the power is sent to a side that has not driveshaft attached and none to the side that has a driveshaft.. so you GO nowhere.

Reduction in the axles have no controls mechanical or otherwise. They are full-time reduction.
 
steve6x6x6

steve6x6x6

Well-known member
Steel Soldiers Supporter
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Location
Winter Haven, florida
lesrrt said:
I wonder if there was a way to disengage the front axle from the permanent AWD drive status. That would seem likely the most drag to be freed; thus making more efficient. I am new and just learning these vehicles. Are the front axles 2:1 ( 1:7) reducers computer controlled? If there was some way to open the front drive up without hindering the safety or original characteristics of what the MV was originally designed for. AWD drive cars and some med duty vehicles have this via the computer. One could take out the front and/or the rear driveshafts to make an experiment. Probably a way to shunt the computer software to allow this. It just would be nice to see if this would render a better result in mpg. I work nights, sorry for the ranting, lol! Some good technicians here, Thanks!!
Click to expand...
All of the LMTV's have a transfer case with a power divider, you can forget locking hubs on the front unless you change the T case.
 
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Aernan

Member
510
19
18
Location
San Jose/California
I'm very interested in doing the high speed gear upgrade. What is the best way for me to get these gears? Is buying a complete axle assembly and getting it shipped/delivered still the only option?
 
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Ultimatehellhound

New member
1
0
0
Location
Spartanburg, SC
I have a set of centers with 3.07's and want to swap them with 3.90's if anyone is interested or has some 3.90 centers they would like to sell. In located in Spartanburg, SC so the closer the better.
 
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bikeracer917

New member
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Location
jax, florida
I'm seriously thinking about doing a gear change. I want more mph. My truck is a 2006 a1. It currently does 60mph. But 70 would be pretty nice. Does anyone know a source for a complete set of gears?
Thanks
 
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DiverDarrell

Member
Steel Soldiers Supporter
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Port orchard, WA
I don't want to be the bearer of bad news but you don't want to do 70mph for a whole lot of reasons. First the truck was spec'ed to do 55mph as that max convoy speed. Second your tires are not rated for that speed, meaning that they will heat up beyond what they are capable of and break down the rubber causing a blowout. Maybe not as worrisome with brand new tires, but at $3k each new I doubt you will be running current year tires. Now let's say you have an accident and it's found you were exceeding the speed rating, a lawyer (not yours) is going to have a big smile. The proper reason to want the high speed gears is so that when running 60 your not on the rev limiter and get better mpg.

Safety rant over. I have high speed gears in my truck and can tell you first hand that 70 is sketchy as F. You will find out just how much your truck can shake shimmy and wander. It's a white knuckle experience. For me 60 is fast enough and my tires will be at max psi when I do it (above ctis highway). Some tires have a max speed of 55 others 60 make sure you know what you have.
 
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scottmandu

Active member
822
36
28
Location
Texas
Run the goodyears and your tie issue is fixed. I run 75 on my LMTV and have has zero issues except less trips to the fuel station.
 
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