CK5
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CUCV mild usage build. Nothing radical here, move along now.

My 1984 K20 used to get 13-15 mpg with the TH400, 4.10 gears and 37" goodyears. But it was gutless with that gear/tire combo.
 
I see 20mpg posted online quite frequently. Don't really believe that but I was hoping for around 15mpg.
I really dig this truck. Great approach on the build. I always appreciate the quality of your work. Subscribed.

In 270k bone stock original form, my suburban got 18ish in town, and 21 on the highway. One time I got 23. Another time I got 15; it was probably was using all 130hp at the time.

After a lift, tires, more fuel and a turbo, I routinely see 13-15 tooling around town. Pulling my project car on a trailer, I got about 12. In ideal conditions and with a light foot, I can get 16 on the highway unloaded.

Enjoy the 6.2. It's a fun engine, and that's a great truck!

David
 
I wouldnt mind 2100 or so rpm at 60, I think that would be a fair balance and probably almost get mine into double digits.

The Jimmy with 37s gets a consistent 17 mpg. But it's got an overdrive. No clue what RPMS I am turning. Gear calculator says just under 2k

I will say at 75 to 80 that milage number drops to around 12 or 13.

That's me filling it up ( it takes forever) to where its fuel is just below the return in the filler hose. And using the GPS speedo on my phone for milage calculations


My 1984 K20 used to get 13-15 mpg with the TH400, 4.10 gears and 37" goodyears. But it was gutless with that gear/tire combo.

I think my RPM's are probably the biggest detriment to the MPG's. On the other hand, I don't want to end up with a gutless turd and probably not gona run out and look for an OD trans. That being said, probably stuck where I'm at for now. Maybe if a 4x 700r4 falls in my lap.


so uh..... whatcha gonna do with the rifle mount?

Sorry, already spoken for. Is it a milspec thing that makes people want that? There are such better options out there now. The stuff they use to put rifles on ATV racks comes to mind.

You have to remember, there are two kinds of diesel owners. Those who don't get as great of fuel economy as the others, and liars.

Martin

Yep, heard that very thing a few times.

I really dig this truck. Great approach on the build. I always appreciate the quality of your work. Subscribed.

In 270k bone stock original form, my suburban got 18ish in town, and 21 on the highway. One time I got 23. Another time I got 15; it was probably was using all 130hp at the time.

After a lift, tires, more fuel and a turbo, I routinely see 13-15 tooling around town. Pulling my project car on a trailer, I got about 12. In ideal conditions and with a light foot, I can get 16 on the highway unloaded.

Enjoy the 6.2. It's a fun engine, and that's a great truck!

David

Thanks for the compliments David. These trucks are fun to build for off road for sure and I really like to do that but driving one every day is just as fun really. I love this old truck. It wasn't so long ago, I had a mid 80's 454 tonner with 37's on that as well. Pretty much just like this but a lot more rust. It caught on fire one morning and pretty much burnt to the ground. That was a great truck. I like having a truck that you can put the bumper on something and push. Or, throw a ton of rock in the back and not have to sweat the damage. Purely a tool through and through. No reason I can't have a nice interior though and make it a little more enjoyable to drive. That's where my focus will be for a while.

I'd be ecstatic with 18 MPG. Don't see that happening less that 4x 700r4 shows up. It may well happen. Just not out looking for any extra personal work right now. Missing the time on my short box build these days.

This summer I intend on building a new garage at the house. That project alone has me in overdrive some evenings and weekends.
 
In my '90 burb I average around 17mpg when I go to VA...6.2, th400. The gear is allegedly a 3:73. :dunno:

That's the only reason I don't do an engine swap on it. ('90 'burb). I keep it under 70 because it is L-O-U-D without an overdrive.
 
Is it "peppy" yet with those gears? Or trouble getting out of its own way?
 
Seems like a fine line with the 6.2
In stock form, very much so. An exhaust and clearer intake path broaden the torque curve on a dual plane J manifold. The slightest bit of timing advance may help, but I wouldn't mess with it since your chain is still nearly new. It's also easy to overdue without a meter.

Mine responded well to gearing. If there's enough highway driving in your future, cruising 65mph at 1900-2100 leaves room for a 3rd gear pass (all but required without a turbo) and won't ruin your fuel economy. Originally, 3.42s and 31s lugged hard on the highway, but sipped fuel.

David
 
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I drive 15 miles one way to the shop every day. All rural highway. Rarely any kind of interstate speeds. Only real option for me is an OD. I could look at better air in takes and so forth but most likely not gona make much difference.

You can pretty much tell at cruising speed, its wound out pretty good.
 
Is it "peppy" yet with those gears? Or trouble getting out of its own way?
it's a long way from peppy. but to me it's just plain fun to drive. It is dependable and runs great, just not fast. It does have 285k miles on it. The 6.2 was designed for mileage per gallon, not power. But it's big, ugly,and loud. Just like me!
 
I filled my pickup to the brim a few weeks ago,and drove it 100 miles,mostly city and rural highway miles,under 50 mph...
If I had been on the interstate going 65,I'm sure the mpg would drop..

It has a 6.2,TH400,and unkown gearing,I'd guess 3:23's or 3:42's,since it will go over 50 mpg in second without hitting the govenor..has 265/75 tires on it now..(which makes it feel more doggy !)..

Went back to the same station and filled it to the brim again,and it took 6.5 gallons to fill it...that comes out to 15.38 mpg...

Maybe the old 6.2 is getting tired,but it seems to start and run good,and I rather doubt doing anything to improve the mpg will make much difference...
I've had more than one truck with straight sixes and small blocks get 15+ mpg,and a few with 454's that came close to that...
 
I've had 454 big block trucks and never had one break 9 mpg.

My Cad 500 big block would average around 10. If I really babied it, I could pull 12 on the hwy. Pulling a load, back to the 7-8 range.

I'm not to terrible worried about it to be honest. It does run pretty good. My biggest concern with it mechanically is the steering has a jerkiness to it. As if it doesn't turn until you have turned the wheel a little further than you want to then the truck catches up to the steering wheel. Now ya gotta correct back the other way with the same jerkiness. As if you are herding it down the road. I'm getting used to it. I'd rather find the issue and correct it. Not easy to find the problem. Checked over everything and a lot of it has been replaced.
 
sounds like a gearbox problem? perhaps the sector shaft is too tight?
 
Or bad steering stabilizer maybe? I've seen people replace all kinds of parts when the stabilizer was bad and binding up.
Knowing how much CUCVs just sit, that's very reasonable.

David
 
Have you done the XJ steering shaft swap/upgrade on this truck? It made a big difference in steering feel on my truck, yours sounds like something worse than a sloppy rag joint however.
 
sounds like a gearbox problem? perhaps the sector shaft is too tight?

Actually, we thought it loose and snugged it up. That seemed to help I guess. Don't want to over do it though.

Or bad steering stabilizer maybe? I've seen people replace all kinds of parts when the stabilizer was bad and binding up.

It has a new steering stabilizer.

Have you done the XJ steering shaft swap/upgrade on this truck? It made a big difference in steering feel on my truck, yours sounds like something worse than a sloppy rag joint however.

Nope, still running the rag joint stock shaft.

It's one of those problems I may need to set up the go pro and take a few videos when driving down the road and see whats going on at speed. Low speed driving conditions you don't notice it at all.
 
interesting drive to the shop today. Driving into a nasty head wind. Couldn't top 45 mph.

Still windy on the way home and 55-60 was so easy.
 

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