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Old 11-28-2019, 06:00 PM   #1
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Overdrive or not?

Hi all...
I have a 1989 F250, LB, c6, an 4:10 gears, 4x4
A 22ft tongue pull

My mileage is awful....7mpg

Im looking at possible overdrive options for towing on flat roads...highways an interstates

Anyone have ideas on mfg, distributors, combos for this???

Ghiaguy
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Old 11-28-2019, 06:48 PM   #2
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Quote:
Originally Posted by Ghiaguy View Post
Hi all...
I have a 1989 F250, LB, c6, an 4:10 gears, 4x4
A 22ft tongue pull

My mileage is awful....7mpg

Im looking at possible overdrive options for towing on flat roads...highways an interstates

Anyone have ideas on mfg, distributors, combos for this???

Ghiaguy
Engine?

I am not surprised. I doubt there's much you can change to raise MPG more than a few percent. I've BTDT.

My old 94 Suburban 5.7 hauling a measly 5500-6000lb loaded trailer was getting5.9 to 6.4 US MPG on average. When I upgraded to the 2011 Sierra 6.0 gasser dually it hauled the same trailer and got 8.4 to 8.7 US MPG. We later purchased our current 5th wheel, a bit longer, MUCH taller and twice as heavy...still getting 8.4 to 8.7 US MPG on average. Worst case 7.1 US MPG in terrible hilly terrain and best of 9.8 US MPG all calculated over hundreds of miles each trip. I don't count the smaller 100 mile trips, too many variables.
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Old 11-28-2019, 06:53 PM   #3
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kd is right, need motor before able to recommend much.
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Old 11-28-2019, 07:05 PM   #4
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A 30 year old Ford truck is probably tired and worn out. You could spend $60k for a newer truck and probably get 2-3 MPG better towing. Getting better MPG probably won't justify any upgrades unless you drive alot of miles towing and plan on keeping your truck for a lot of additional years.
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Old 11-28-2019, 07:16 PM   #5
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Rather than trying to overdrive, see if you can get a locking torque converter. I doubt a truck from '89 has that. If the converter never locks up, the engine will always be turning faster than it needs to. That wastes fuel.
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Old 11-28-2019, 11:32 PM   #6
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We just had this discussion on here recently. I dont believe we were able to find a way to lock up the c6. Im honestly suprised your mileage is as good as it is. Id say your best bet without sinking a ton of money into your 89 would be to retire it and get something way newer with more gears and a lockup tc but, like kd said, i doubt youll see much of an increase. your creature comforts will be way nicer though.
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Old 11-29-2019, 07:16 AM   #7
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7mpg isnt that bad. spending money on a new truck.isnt worth the mileage increase. Im guessing its either a 460 or and 351M. Id free up either engine with an exhaust system and tune her up. New plugs, wires, fuel filter etc. After that drive the wheela.off it. A truck like that is cheap to fix if it tears up an none of the electrical hassle too.
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Old 11-29-2019, 08:04 AM   #8
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https://www.gearvendors.com/index.html
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Old 11-29-2019, 09:08 AM   #9
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Quote:
Originally Posted by Ghiaguy View Post
Hi all...
I have a 1989 F250, LB, c6, an 4:10 gears, 4x4
A 22ft tongue pull

My mileage is awful....7mpg

Im looking at possible overdrive options for towing on flat roads...highways an interstates

Anyone have ideas on mfg, distributors, combos for this???

Ghiaguy
Hi Ghaiguy,

There are multiple factors involved that determine your fuel economy. Before you start spending money to improve economy you need to understand those factors.
  • How fast do you drive?
  • How much is the combined weight of your truck and camper?
  • What engine does your truck have?
  • Is the truck engine healthy and in good tune?

Answers to the above questions might help determine your course of action.
The single biggest factor in fuel economy is speed. If you are driving 75 MPH then 7 MPG is pretty good. If you drive 55 you should get closer to 10-11 possibly more.

Maybe all you need to get better economy is slow down.

I had a '72 F250 with the 390, 4.1 gear, manual non overdrive transmission. I carried a camper for a total weight of about 9500 lbs. If I drove 55 MPH I got 11 MPG. If I drove ~62 MPH I got 9 MPH. Speeding up 7 MPH cost me 18% more fuel! Although I never drove it 70 MPH with the camper up I'm sure that about 7 MPG or worse would have been the result.

A Gear Vendors was mentioned. I am a big fan of Gear Vendors. It is a excellent for heavy loads when you have a transmission with wide gear ratios like the C6. By splitting gears you can keep your engine in its power zone allowing you to climb mountain passes at a much higher speed and lower engine RPM's. I had a 1988 Motorhome with Chevy with P32 chassis and TH475 transmission. I loved the Gear Vendors for its ability to improve overall performance in the mountains. It improved my mileage by about 5% maybe. At $3 per gallon you would have to tow your trailer more than 100K miles to get your money back!

See here for a Gear Vendors for your truck:
https://www.gearvendors.com/f2wd3s.html
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Old 11-29-2019, 01:04 PM   #10
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You are getting all it has now. Towing in a higher gear will kill that motor. Lugging is very hard on them.

Wind resistance at highway speed is far more pull on the truck than the weight. I have two trailers that are about the same size but one weighs 2500 pounds more than the other and there is zero difference in mileage between them.

I have a 2016 F250 with a 6 speed tranny, locking converter and overdrive and I get 8.5 MPG towing no matter whether it is uphill or flat land. With a 30 MPH headwind it has gone as low as 4.5 MPG, With the same tailwind it was almost 14 MPG but it always averages out at 8.5 Your older engine will live longer if you keep the RPMs up and gas mileage will not be any different.

I had an 85 Chevy once that had 410 gears and the old 3 speed without O.D. and it turned 3500 RPM at 60 MPH, still got the same mileage as a buddy with the same truck and 355 gears but mine would pull much harder.
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Old 11-29-2019, 01:26 PM   #11
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The number one reason for poor fuel economy when towing is the terrible aerodynamics of towing a huge box at highway speeds.

Overdrive will not help in any appreciable way. My truck, a 6.0 Chevy gasser, gets the same fuel economy whether I tow in OD, or if I lock it in D. The only thing that changes is RPM and trans temp.

As others have said, for that year truck and its mileage, you're about average.
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Old 12-02-2019, 10:19 PM   #12
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I can't say anything about od but I will say this. I drive a 2006 f150 and tow a funfinder 210. If I keep my speed at 55 to 60 I will get 11 mile to the gallon , if I run 70 my mileage will drop to 8 to 8. 5 per gallon. As others have said the wind resistance of many camping trailers are not good. They are made for interior space more than towing resistance.
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Old 12-04-2019, 04:15 PM   #13
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Od or not...

Hi guys im bak

Ok ... 351w, c6, 4:10 4x4...

Yes have upgraded motor with headers an flow thru exhaust...

I also was still havin vacuum issues...
Replaced all lines an engine is oprating much better...

I did go to that site u suggested for a compatible od unit an its cost is more than the truks worth...lol. In fact i paid 400 for my truk an the od is 700!!!

So im rethinkin that

I remember in 60’s an 70’s there were od unit available much less expensive an i wonder now y so much?

Anyway i agree that the trailer is taller than truk cab so im thinkin put a spoiler/ wind deflector on cab an c how that goes... i think it should help as wind will b redirect to “slide over” an up above trailer so less drag....

Thots?

Thx for sharing!!

Ghiaguy
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Old 12-04-2019, 04:19 PM   #14
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Agree

Quote:
Originally Posted by dustyone View Post
I can't say anything about od but I will say this. I drive a 2006 f150 and tow a funfinder 210. If I keep my speed at 55 to 60 I will get 11 mile to the gallon , if I run 70 my mileage will drop to 8 to 8. 5 per gallon. As others have said the wind resistance of many camping trailers are not good. They are made for interior space more than towing resistance.
Yu r correct.... 55-60 the engine isnt workin as hard...@70 it has many additional factors to slow it down thus makin it work harder:

Drag resistence is a lot greater
Uses more fuel at higher speeds

Im keepin this in mind for sure

Ghiaguy
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