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Old 02-09-2019, 09:35 AM   #1
5Tractorguy
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What are you 1-ton guys getting for MPG?

I think after 8 years I finally licked the engine/trans problems with my 1-ton. Some may remember my brief thread about swapping in a TBI and ECM from a '91 3/4ton Chevy.

Well I did, it runs pretty darn good now but only gets 8 - 8.5mpg. And that's without putting my foot in it and unloaded. (350 and TH400, probably 4:10's. About 2500rpm at 55mph).

I know I shouldn't complain being what it is, but I'm finicky about how stuff runs so curiosity gets the best...

My dad said he used to get about 9mpg with the '91 so I'm assuming at this point it has to do with how the ECM is programmed for the specific truck.

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Old 02-09-2019, 12:30 PM   #2
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Re: What are you 1-ton guys getting for MPG?

mine gets 16-17......lq9/nv4500/4.10s...if I keep my feets outta it
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Old 02-09-2019, 01:16 PM   #3
57NAPCO
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Re: What are you 1-ton guys getting for MPG?

I have a few 1 tons but with big blocks and I have never really checked MPG but I’m guessing around 10, would not surprise me if you were getting 8 with the 350 due to the fact it might be working it’s arse off pulling that big fella around. Just an opinion is all.
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Old 02-09-2019, 01:18 PM   #4
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Re: What are you 1-ton guys getting for MPG?

1981 Flat deck dually LQ4/4l80 4.10 diff gears, 30inch tall tires.
Truck weighs 7300 lbs. empty, which doesn't help.
Avg MPG is 10 - 11mpg

OP how is the wind noise with that headache rack?
had something similar and the wind noise was driving us crazy and making us deaf, took it off and made one more open and the reduction in wind/whistling noise was a major improvement
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Old 02-09-2019, 03:11 PM   #5
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Re: What are you 1-ton guys getting for MPG?

yeah ...back when my had the 350/sm465/4.10s it would be lucky to get 10mpgs with a strong tailwind
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Old 02-09-2019, 03:14 PM   #6
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Re: What are you 1-ton guys getting for MPG?

My 1990 gmc 4x4 crew cab 350 tbi with headers and dual exhaust ,th400, .410's gets 11-12 on highway trips.

Im running 35's so my highway rpm's are prolly a little less than yours at the same speed
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Old 02-09-2019, 03:16 PM   #7
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Re: What are you 1-ton guys getting for MPG?

Also your bed , mirrors , and attachments prolly have more wind drag
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Old 02-09-2019, 05:44 PM   #8
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Re: What are you 1-ton guys getting for MPG?

Quote:
Originally Posted by 57NAPCO View Post
I have a few 1 tons but with big blocks and I have never really checked MPG but Iím guessing around 10, would not surprise me if you were getting 8 with the 350 due to the fact it might be working itís arse off pulling that big fella around. Just an opinion is all.
You're probably right about that. It is a lot of truck for the engine never mind pulling a loaded trailer or filling the bed. Good portion of the time driving the hills around here empty you're at least at 1/2/+ throttle.

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1981 Flat deck dually LQ4/4l80 4.10 diff gears, 30inch tall tires.
Truck weighs 7300 lbs. empty, which doesn't help.
Avg MPG is 10 - 11mpg

OP how is the wind noise with that headache rack?
had something similar and the wind noise was driving us crazy and making us deaf, took it off and made one more open and the reduction in wind/whistling noise was a major improvement
Well, its got some. If there is a head wind you definitely feel it drag. But as for noise it's not too bad with the windows down. The mirrors are the noisiest part because the wind will catch the brackets just right at a certain speed and makes them whistle... go figure. I really like the look of the truck with it off, but since this gets used as a work truck, the headboard is a must.

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My 1990 gmc 4x4 crew cab 350 tbi with headers and dual exhaust ,th400, .410's gets 11-12 on highway trips.
I used to be at 10 - 10.5 before I changed the throttle body and computer. But, it also ran like crap then and had no power. So I figured at least at 8.5 I have my power back and a usable truck again. Who knows, could have been running lean then...

Just thought maybe something was off and it was dumping too much fuel in.
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Old 02-09-2019, 06:10 PM   #9
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Re: What are you 1-ton guys getting for MPG?

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Originally Posted by 5Tractorguy View Post
I really like the look of the truck with it off, but since this gets used as a work truck, the headboard is a must.
Would it reduce the effectiveness of the headboard if you trimmed it down? Trace out the shape of the cab rear on the headboard and reduce it to that. There's welding shops here that would do that for about two Franklins in the pocket, and make it look quite nice.
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Old 02-09-2019, 06:22 PM   #10
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Re: What are you 1-ton guys getting for MPG?

Used to get 7-8 mpgs with the old 350/350 combo and 4.56 rears
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Old 02-09-2019, 07:02 PM   #11
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Re: What are you 1-ton guys getting for MPG?

my '85 gets 5 or 6....downhill
do i win something?
these are 1 tons, mileage and good are an oxymoron....
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Old 02-09-2019, 08:13 PM   #12
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Re: What are you 1-ton guys getting for MPG?

i recall guys back in the day installing the LUND cab sun visor and saying they lost 2-3 mpg with it on there . i would bet that headboard above the cab does NOT help any . i bet if you cut some holes in it or changed the top 1ft or so to expanded metal if you still need it that tall would help a lot .

nice rig by the way . . . . and fisher speedcast for the win . . 8 or 9ft blade ?

i have a 8ft and a 9ft blade for my truck .
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Old 02-09-2019, 09:55 PM   #13
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Re: What are you 1-ton guys getting for MPG?

79 1 Ton dump- 350/sm465/ 4:10 rear- never checked but so low was almost gallons to the mile. Always joked you hit a steep hill loaded down don’t what went down quicker the speedo or gas gauge.
Same truck, swapped to 468/nv4500- 10.5 engine not even broken in
92 1 ton dump- 454 tbi/ nv4500 4:56 4x4- gets 9-9.5. Doesn’t matter what. But does weigh 8,000 empty
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Old 02-09-2019, 10:34 PM   #14
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Re: What are you 1-ton guys getting for MPG?

My 74 got best one time 10.7 mpg doing 60. 350 sm465 and either 4.10 or 4.56.
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Old 02-09-2019, 11:13 PM   #15
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Re: What are you 1-ton guys getting for MPG?

Quote:
Originally Posted by kipps View Post
Would it reduce the effectiveness of the headboard if you trimmed it down? Trace out the shape of the cab rear on the headboard and reduce it to that. There's welding shops here that would do that for about two Franklins in the pocket, and make it look quite nice.
Would unfortunately! Being a welder by trade I've though about it a time or two, but if I pick up a load of tractor stuff and fill the bed, more often than not I need all that height.

Quote:
Originally Posted by Big Moose View Post
Used to get 7-8 mpgs with the old 350/350 combo and 4.56 rears
Well, I guess I'm right on the money!

Quote:
Originally Posted by dieseldawg142 View Post
my '85 gets 5 or 6....downhill
do i win something?
these are 1 tons, mileage and good are an oxymoron....
Hot dang, I feel pretty good now!

I know, but like I said, I'm curious...


Quote:
Originally Posted by sweetk30 View Post
i recall guys back in the day installing the LUND cab sun visor and saying they lost 2-3 mpg with it on there . i would bet that headboard above the cab does NOT help any . i bet if you cut some holes in it or changed the top 1ft or so to expanded metal if you still need it that tall would help a lot .

nice rig by the way . . . . and fisher speedcast for the win . . 8 or 9ft blade ?

i have a 8ft and a 9ft blade for my truck .
Thanks k30! Has a 8ft plow. Since restored only plowed 2 winters when a friend of my fathers plow truck bit the dust.
As I've said, head board has to stay. I love the look with out! But I like having the back of the cab not smashed more...


Quote:
Originally Posted by Tiger Joe View Post
79 1 Ton dump- 350/sm465/ 4:10 rear- never checked but so low was almost gallons to the mile. Always joked you hit a steep hill loaded down donít what went down quicker the speedo or gas gauge.
Same truck, swapped to 468/nv4500- 10.5 engine not even broken in
92 1 ton dump- 454 tbi/ nv4500 4:56 4x4- gets 9-9.5. Doesnít matter what. But does weigh 8,000 empty
Wow, I'd think 10.5 is pretty darn good for a 468c.i.


Aside from curiosity, I'm supposed to be taking a trip to PA for a plow day weekend in April if I finish a tractor I'm working on... Plan is to take my '77 K25 down, but I always liked driving the 1-Ton, bigger truck, more room on the back for any stuff I find down there (good stereo too). But being able to squeeze 11-13 out of the 350 in the K25, I think that's going to win.
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Old 02-10-2019, 12:12 AM   #16
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Re: What are you 1-ton guys getting for MPG?

Headboard could be reworked to follow the shape of the cab...here's the one I built for mine...
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Old 02-10-2019, 12:16 PM   #17
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Re: What are you 1-ton guys getting for MPG?

" Thanks k30! Has a 8ft plow. Since restored only plowed 2 winters when a friend of my fathers plow truck bit the dust.
As I've said, head board has to stay. I love the look with out! But I like having the back of the cab not smashed more... "

like i said even if you change the upper material for more air flow or cut some holes in what you have it would help .
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Old 02-11-2019, 01:05 AM   #18
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Re: What are you 1-ton guys getting for MPG?

1987 TBI454/TH400/4.10 CC Dually and I get 9-10 consistently. I can pull out just over 11 on pure highway if I can keep it down to 65mph.
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Old 02-11-2019, 10:12 AM   #19
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Re: What are you 1-ton guys getting for MPG?

I've been modifying my 85 K20 trying to get my milage down to a more realistic mpg.
I swapped the stock axles for a heavier Dana 60 and 14 full float axle. These were NOS military finds for cucv application so I got the free benefit of dropping to 4:56 gears instead of the 4:10's.
These really make the underpowered 350 scream with the turbo 400! I also added a drag inducing Lund Moon Visor, Hickey Push Bar and ill fitting camper shell. So far I've only been able to get it down to about 8-9 mpg. I live in the desert so I don't have need of a plow...I'll have to think of something more practical.
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Old 02-11-2019, 03:53 PM   #20
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Re: What are you 1-ton guys getting for MPG?

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Originally Posted by SunSoaked View Post
I've been modifying my 85 K20 trying to get my milage down to a more realistic mpg.
I swapped the stock axles for a heavier Dana 60 and 14 full float axle. These were NOS military finds for cucv application so I got the free benefit of dropping to 4:56 gears instead of the 4:10's.
These really make the underpowered 350 scream with the turbo 400! I also added a drag inducing Lund Moon Visor, Hickey Push Bar and ill fitting camper shell. So far I've only been able to get it down to about 8-9 mpg. I live in the desert so I don't have need of a plow...I'll have to think of something more practical.
I'd love to find one of those push bars for my dually.
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Old 02-11-2019, 04:09 PM   #21
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Re: What are you 1-ton guys getting for MPG?

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I'd love to find one of those push bars for my dually.

Well today is your lucky day! I found one for ya! I already texted him, it's the same as mine and you're both in Phoenix. Go get it before it's gone! That's what I did...from Yuma.
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Old 02-12-2019, 09:36 AM   #22
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Re: What are you 1-ton guys getting for MPG?

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I'd love to find one of those push bars for my dually.
DieselSJ-
Here it is. I'm not even going to charge you a finder's fee! Lol. If you don't get it, I will. These are getting hard to find.
602-692-6198
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Old 02-12-2019, 11:36 AM   #23
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Re: What are you 1-ton guys getting for MPG?

The k25 on the left gets 14-16 with 3:73's and a 4.8 LS and a th350.

C35 on the right gets 8-10 driving like a grandpa (hey it looks the part!) with a 350 th400 and 4:10's.
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Old 02-12-2019, 01:27 PM   #24
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Re: What are you 1-ton guys getting for MPG?

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Originally Posted by SunSoaked View Post
So far I've only been able to get it down to about 8-9 mpg. I live in the desert so I don't have need of a plow...I'll have to think of something more practical.
The desert eh?? Sand paddle tires! That outta turn the 'ol MPG to GPM...

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DieselSJ-
Here it is. I'm not even going to charge you a finder's fee! Lol. If you don't get it, I will. These are getting hard to find.
602-692-6198
I do like the look of those push bars on the K series, makes 'em look a bit more rugged.

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The k25 on the left gets 14-16 with 3:73's and a 4.8 LS and a th350.

C35 on the right gets 8-10 driving like a grandpa (hey it looks the part!) with a 350 th400 and 4:10's.
Thanks for the reference numbers Bob. Really like that C35... I've had a thing going for 1-ton regular cab pickups lately, dually and single wheel.
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Old 02-12-2019, 02:06 PM   #25
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Re: What are you 1-ton guys getting for MPG?

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Well today is your lucky day! I found one for ya! I already texted him, it's the same as mine and you're both in Phoenix. Go get it before it's gone! That's what I did...from Yuma.
I love you man!

I mean that in a total brotherly way, not some weird want to have your baby way.
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