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FMTV gearing

m37charlie

New member
17
5
3
Location
Anchorage, AK
Please forgive these questions, but I don’t spend much time on this forum. However I am highly knowledgeable re mechanical engineering, military vehicles in general and know a lot about FMTVs - but not everything.
1) Is there a 2.867 diff gearset in existence, intended for MRAPs, that will give 5.733 installed in a FMTV? If so, is it completely unobtainium?
2) Does anyone have experience with operating a heavily loaded (camper with lots of water, fuel, junk) FMTV, especially a 6x6, with 6.14s in rough terrain? Are there plausible situations where a low range in the transfer case would be highly desirable? Especially if gears were 4.5% taller? What about 11% taller (5.87s plus 14.00R20)?
Remember a fully loaded LMTV with a 15’ camper might gross at ~25000 lb, a MTV with 20’ camper at up to 30000 lb. The M-H MVG 1150 can be ordered, very nice 2.47 low range, but unfortunate 1.09 high range. And of course $$$$. It is a bolt in apparently except for driveshafts. And extra plumbing for high-low shifter. 1.09 ratio makes 5.87s especially desirable.
3) any progress on front air locker?
4) do FMTV wheels come stock with internal beadlocks? If not, or if uninstallable, are appropriate Hutchinson wheels available? If so, only brand new or also surplus?
5) on the 4x4 LMTV, is there any reason why 16.00R20s are a really bad idea? Other than COG and roof height 3” higher, ridiculously heavy, speed limited to 55?
6) what’s the interaxle distance on the 6x6? Has to be at least 1400mm to accommodate 16.00s.
Not interested in driving >60mph ever. Am interested in driving as slow as possible over rough terrain to protect camper contents and keeping rpms as low as possible at 60mph because of noise, fuel consumption etc. Driving at 2400 rpm for thousands of miles is not on my list of happy thoughts. Though I guess 2140 at 60 mph is not quite as bad, but 18-1900 much better.
Again, sorry for all the questions.
 
Last edited:

Third From Texas

Well-known member
2,706
6,338
113
Location
Corpus Christi Texas
1) If I recall, Bryce has the 2.8x gears. A few folks on here run them.

3) Last I heard, Bryce was the last one persuing that but he stopped and shifted to converting AxelTech axels to retro fit (they have disc brakes, taller gears, and lockers already installed) but they obviously are not a direct bolt-on solution.

5) Again, there are a few here who run 16R20's (see img).

58a9b99ec85bb1e64b43b8630ebe6562.jpg

And there is a fellow local to me with aM1079 running 53's. I have a great pic somewhere of him buried to the axels in mud. Heh
 

MrMikey4026

Well-known member
281
416
63
Location
Eatonville Washington
Please forgive these questions, but I don’t spend much time on this forum. However I am highly knowledgeable re mechanical engineering, military vehicles in general and know a lot about FMTVs - but not everything.
1) Is there a 2.867 diff gearset in existence, intended for MRAPs, that will give 5.733 installed in a FMTV? If so, is it completely unobtainium?
2) Does anyone have experience with operating a heavily loaded (camper with lots of water, fuel, junk) FMTV, especially a 6x6, with 6.14s in rough terrain? Are there plausible situations where a low range in the transfer case would be highly desirable? Especially if gears were 4.5% taller? What about 11% taller (5.87s plus 14.00R20)?
Remember a fully loaded LMTV with a 15’ camper might gross at ~25000 lb, a MTV with 20’ camper at up to 30000 lb. The M-H MVG 1150 can be ordered, very nice 2.47 low range, but unfortunate 1.09 high range. And of course $$$$. It is a bolt in apparently except for driveshafts. And extra plumbing for high-low shifter. 1.09 ratio makes 5.87s especially desirable.
3) any progress on front air locker?
4) do FMTV wheels come stock with internal beadlocks? If not, or if uninstallable, are appropriate Hutchinson wheels available? If so, only brand new or also surplus?
5) on the 4x4 LMTV, is there any reason why 16.00R20s are a really bad idea? Other than COG and roof height 3” higher, ridiculously heavy, speed limited to 55?
6) what’s the interaxle distance on the 6x6? Has to be at least 1400mm to accommodate 16.00s.
Not interested in driving >60mph ever. Am interested in driving as slow as possible over rough terrain to protect camper contents and keeping rpms as low as possible at 60mph because of noise, fuel consumption etc. Driving at 2400 rpm for thousands of miles is not on my list of happy thoughts. Though I guess 2140 at 60 mph is not quite as bad, but 18-1900 much better.
Again, sorry for all the questions.
2.87 gears are available, just gold plated! 3.07gears are also plated with unafforduem.
 

m37charlie

New member
17
5
3
Location
Anchorage, AK
5.733 x 6.93 1st gear times tire diameter correction factor for 395s vs “standard” Landcruiser diameter 31.9” comes out to ~27:1. Not good, ignoring torque converter factor of ~2:1. That is why I continue to dwell on low range possibilities. The vehicle is physically large, heavy, underpowered for weight etc etc. All of which encourage lower low gears.
As far as I think, 80-100:1 is minimum.
 
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