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

[SammyChevelleTypeS3]

I enjoy it. More like you are part of the machine, than just gliding in a near silent computer on wheels. I enjoy the smell, and the noise, and the "soul" of the machine. Some vehicles have one it seems and some dont.

I think I have chronicled everything with it so far, of nearly everything.

I did do a 12volt conversion.

I enjoy it. More like you are part of the machine, than just gliding in a near silent computer on wheels. I enjoy the smell, and the noise, and the "soul" of the machine. Some vehicles have one it seems and some dont.

I think I have chronicled everything with it so far, of nearly everything.

I did do a 12volt conversion.

I have owned a couple machines we were attatched to , seemed like they were a part of the family. Its still hard for me to accept letting my last one go in 2019 during my last health issues. It was the right thing to do. I like your machine. It does look like a lot of fun and could have plenty of use for some work and more play.

 

[demarpaint]

I'm glad you went for it, drive it in good health!!!!

 

[bullwinkle]

There are a few bugs. Need to change the fuel pump. I think it is backfeeding into the tank when not starting in maybe two weeks. Unlike what some think, this can only run on diesel, not cooking oil like the internet would have some think. I reckon used oil could be filtered and add to the diesel, but not worth the risk.

That's either the check valve on the return line on the injection pump, or the mechanical fuel pump (if it doesn't have the electric FP). My F-450 does the same thing if it sits longer than a month or 2. When I had my '93 GMC C3500 6.2, I modified the electric fuel pump control to run as long as the glow plugs were on with an extra relay, that helped on that truck.

 

[burbguy82]

When I had my '93 GMC C3500 6.2, I modified the electric fuel pump control to run as long as the glow plugs were on with an extra relay, that helped on that truck

I have a spare mech pump I got for like 20 bucks....but have thought about going with an electric pump from a 93 6.5.

It would aid in fuel filter change priming, eliminate a bunch of lineal feet of fuel line and routing, eliminate fuel mixing in the engine oil case if their is an internal pump leak, give a more constant fuel pressure, etc.

I cannot see very many drawback to the system, if installed properly.

I actually have a Delhi pump kit for a 93 6.5 in my cart on Rock Auto, along with the proper connector. I would of course have to make my own wiring harness, but that is not too bad.

Could you just run the pump constantly while running via switch? Provided that you turned it off at key off, or would the DB2 pull the requisite fuel without a lift?

 

[Stumpy]

Most of those military vehicles are really shot by the time they reach auction. This one sounds ok.

A lot of the Alabama National Guard Chevy's were used lightly and I see with some frequency to this day. 24 volt electrics if I remember correctly.

 

[joekingcorvette]

That is one sweet looking truck!

 

[burbguy82]

custom made bracket for 7 pin harness

 

[burbguy82]

fuel pump! if it was not 4wd, it would be easy

had to remove and reinstall, missed the pushrod alignment.

purshrod looking good

 

[panthermike]

I enjoy it. More like you are part of the machine, than just gliding in a near silent computer on wheels. I enjoy the smell, and the noise, and the "soul" of the machine. Some vehicles have one it seems and some dont.

I think I have chronicled everything with it so far, of nearly everything.

I did do a 12volt conversion.

Absolutely agree on this. My favorite vehicle that I owned was a '77 F250 Highboy, such an engaging(sometimes tiring) endeavor. But I always felt so good driving that truck.

 

[Fabulous50s]

I've always been a fan of electric pusher fuel pumps. Aids in starting and really simplifies fuel filter changes.

No more excessive cranking just to run the mechanical pump to get fuel to injection pump.

On all my diesel tractors, I run an electric pump at the tank with just a simple coarse screen filter ahead of the pump. Then the pump pushes through the water separator and then a spin-on filer. I run either a very small (3/16, or ⅛") return line or an orface tee'd in just before the injection pump inlet.

This way with water separator/filter replacement, I simply key on and the pump pushes fuel into the dry filters and the air makes it's way to the Tee at injection pump inlet, and back to the tank. This keeps 1 or 2 psi at the injection pump inlet and air always goes into the return to the tank.

I use the same setup on my gasoline carb'd engines. Small return or an orface to give some restriction and therefore a bit of pressure at carb/injection pump.

 

[burbguy82]

The Dodge in my sig gets new gears this winter.

With the granny low, and still super short 2nd out of the NP-435, it's far more capable than anything I'd throw at it with a 4.10 rear. Moving to 3.54 so I can get some highway capability.

Feel like these old trucks were all about the numbers game rather than practicality. Just like the new ones. Don't need to pull a house down. Just need average capability.

Admittedly, this old truck is still more practical as a truck than anything today.

the splitter might be the way to go for you......maybe not, costs would be close assuming to did none of the work.

 

[emmett442]

I've considered. But the cost difference is too great.

Gears, bearings, shims, seals will cost me maybe $500. A splitter setup is a few thousand on its own, plus I'll need to have a driveshaft made.

A move from 4.10 to 3.54 will put me at 70mph @ 3000 rpm. That'll do just fine, I think.

 

[burbguy82]

I've considered. But the cost difference is too great.

Gears, bearings, shims, seals will cost me maybe $500. A splitter setup is a few thousand on its own, plus I'll need to have a driveshaft made.

A move from 4.10 to 3.54 will put me at 70mph @ 3000 rpm. That'll do just fine, I think.

I think it would be fine also. Of course you would lose a bunch of low end. 3.54 is a worthy jump from 4.10. Good luck.

There is value with read end rebuild also, so there is that to your point

 

[Brons2]

The Dodge in my sig gets new gears this winter.

With the granny low, and still super short 2nd out of the NP-435, it's far more capable than anything I'd throw at it with a 4.10 rear. Moving to 3.54 so I can get some highway capability.

Feel like these old trucks were all about the numbers game rather than practicality. Just like the new ones. Don't need to pull a house down. Just need average capability.

Admittedly, this old truck is still more practical as a truck than anything today.

I don't see any signature? Is it a first gen Cummins?

 

[Rmay635703]

I don't see any signature? Is it a first gen Cummins?

Yeah this site has always had a defect on iOS that regardless of your view type desktop/mobile signatures aren’t viewable

I think it would be fine also. Of course you would lose a bunch of low end. 3.54 is a worthy jump from 4.10. Good luck.

There is value with read end rebuild also, so there is that to your point

The guy with the “40mpg Buick Roadmaster “ claimed he could swap rear ends in under a half hour.

When commuting he had a <2.5 rear, when towing he just swapped in a different rearend from his collection to match the load size. He claimed to have picked up rear ends for <$200 each

 

[burbguy82]

“40mpg Buick Roadmaster “ claimed he could swap rear ends in under a half hour.

who is that....I would like to see that done in less that 1\2 hour.

 

[Rmay635703]

who is that....I would like to see that done in less that 1\2 hour.

I think I’ve found out why it was possible, but he found the rear gear ratio doesn’t matter with a properly geared manual transmission over an auto.
I’m trying to find his original thread

 

[emmett442]

I don't see any signature? Is it a first gen Cummins?

Close:

 

[supton]

I think I’ve found out why it was possible, but he found the rear gear ratio doesn’t matter with a properly geared manual transmission over an auto.

Interesting, although right away it may be hard to duplicate his mpg findings. I'm not sure how many want to do pulse and glide while driving--someone else, wanting to just flow with the traffic or otherwise set cruise, may find more conventional mpg findings. Pure swag on my part (but his findings are interesting, I'll say that).

 

[Rmay635703]

Interesting, although right away it may be hard to duplicate his mpg findings. I'm not sure how many want to do pulse and glide while driving--someone else, wanting to just flow with the traffic or otherwise set cruise, may find more conventional mpg findings. Pure swag on my part (but his findings are interesting, I'll say that).

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.