Old 6.2L GM military truck ... Talk me out of this......

Rmay635703 said:
His original setup many years ago (at this point decade +) was an automatic, some body/aero mods and changeable rear axle ratios so he could tow or highway cruise. From memory That airplane rear netted him 40mpg+ without any fancy driving.

If you have an overhead hoist, quick connects and pulse tools maybe it would be worth swapping the rear axle between hauling season and cruising season (from what I remember he towed a lot certain months of the year so the axle stayed put much of the time)
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It's a pretty cool idea, and low buck, if you can do the work. Almost like summer and winter tires. Instead of finding the best compromise... just go for the best in the situation. [Sorta--there was probably times when he had towing gears but wasn't towing, just like plenty of bare clean roads in winter time. Best most of the time.]
 
atikovi said:
Can it even do the speed limit? Engine probably redlines at 50 mph. Whenever I pass a convoy of military trucks, they are doing about 45, and even at that speed the engines seem to be screaming.
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the pictures suck, but i usually cruise at 55. interestingly, the speedometer works and is accurate, most of the time, sometimes it is 5 mph high..oil stays at a steady 40ish at speed, coolant temp is really low, like 140.....i think I need a winter bra.
 
burbguy82 said:
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the pictures suck, but i usually cruise at 55. interestingly, the speedometer works and is accurate, most of the time, sometimes it is 5 mph high..oil stays at a steady 40ish at speed, coolant temp is really low, like 140.....i think I need a winter bra.
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Although I have never followed t-case modifications it does appear that the np205 t-case has a 1.96-1 low and can accept a twin stick mod.

If you find that you NEVER use low range a swap to a 205 and a twin stick mod would allow you to more cheaply get a 4wd low range of 4.56 or more and an airplane gear range in 2wd only (being a little creative, but being a 2 range you loose the creeper gear in 4wd)

It looks like there are so called automatic and even 3 gear mods for various GM t-cases but all look rather involved and unknown on price.
 
Rmay635703 said:
Although I have never followed t-case modifications it does appear that the np205 t-case has a 1.96-1 low and can accept a twin stick mod.

If you find that you NEVER use low range a swap to a 205 and a twin stick mod would allow you to more cheaply get a 4wd low range of 4.56 or more and an airplane gear range in 2wd only (being a little creative, but being a 2 range you loose the creeper gear in 4wd)

It looks like there are so called automatic and even 3 gear mods for various GM t-cases but all look rather involved and unknown on price.
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thanks for the info. i will look into it.
 
4wheeldog said:
I would bet the thermostat has a fairly large bypass hole by design. So a radiator blocking strategy might be a good solution.
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it does have a hole, maybe less than an 1/8 inch. There is a winter canvas bra, that the military issued with the truck, for use in the winter to cover the radiator. i just put me a piece of foam which seems to help. thanks
 
Rmay635703 said:
His original setup many years ago (at this point decade +) was an automatic, some body/aero mods and changeable rear axle ratios so he could tow or highway cruise. From memory That airplane rear netted him 40mpg+ without any fancy driving.

If you have an overhead hoist, quick connects and pulse tools maybe it would be worth swapping the rear axle between hauling season and cruising season (from what I remember he towed a lot certain months of the year so the axle stayed put much of the time)

My 2wd 82 diesel suburban had a 2.8 rear and a 5 speed granny/ overdrive. Had to really slip the clutch with an 18ft enclosed trailer but most of the time I had the rear seats down, a trailer hitch support slung on the rear for the tent and flirted with 30mpg at 55mph. I had 15” tires, and the truck sat quite low compared to the ops setup.

The ops non-locking turbo 400 with big wheels likely has a MPG sweet spot with a very different rear end depending on his typical speed. Guessing 3.02-3.5ish depending on how much she slips.
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i am not sure of mpg just yet.
 
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