Only thing with an o/d is you'll not get into 5th o/d much if doing any towing for any fuel gains, other then running empty or not towing. I'm taching in 5th o/d 1800 at 60 or 2200 at around 70 mph and have gotten as much as 14 mpg on a 500 mile trip back from Vegas with 32'' tires 4:10 out back. Plus with my old motor and a bunch of crap in the bed with having a cab high camper shell.

I drive with the use of a vacuum gauge. The old mileage minder that shows when your wasting fuel and good for shift points so as not to bog the motor down. Plus with a tach all aides in my driving to get the best all round fuel mileage.

I got use too driving with a tach and shifting points going up & down the steep hills in Vietnam Mang Yang pass which was a road of steep switch backs up the mountain pass. As most all times we were over loaded 5 ton cargo 8 wheelers.
The most wt. was 53,000lbs and if you missed a spilt shift you'd end up stopped. Then have to drop back in 1st under to get going again. This was bad, but most the time the rear truck would come up and help push you to get back up to speed
to shift to the next higher gears as not to hold up the convoy.


So when adding a c/o camper no more wild off roading around with camper on.
This was when, I added a tach & the mileage or motor minder and used them ever since..
orich

 

Fuel milage is gonna suck when towing regardless... but when not towing that OD ratio will produce better milage and this change won't sacrificing any towing power.

 

DO NOT expect to match the numbers that orich is saying, he has a super secret device hooked up to deliver those and he has a patten on it.



John

 

Yup it takes money to get better fuel mileage and a lot of tinkering.

Operate a motor vehicle with in the best power band with Tach & a Vacuum
meter, Plus correct carb jetting. A electronic speedometer dialed in for the correct mileage/speed reading.

Oh and my latest toy is a installed Cruise Control Unit that, I have yet to tested out for any fuel mileage yet. And yeah it's on a stick tranny and, I just love it on the freeway. The ol Type ll diabetes has done a number on my feet loosing the most of the feeling. So sometimes it's hard to maintain one speed. As, I can't feel the pressure I'm pushing on the gas peddle any more. This cc unit helps keep me in the drivers seat.

Plus, I'm not ready to turn my truck over to my son just yet!

I'm still mobile and have money for tinkering with ol blue, and it gives me something to do.

Oh the secret Formula-xx heading off to the Patten office now.

orich

 

I see the exact same thing when (and if) I get to drive my brother's highboy. It is set up the exact same way and easily gets 14 mpg driving 70.

 

HI all. Is it fun to driver? yaHHHHH then just do it dude

 

My old '73 F-250 Highboy with 4x4 390 and 4.11(4.10)s got 5 mpg. I've never owned a 300 I6 truck, but my '78 C-30 Chevy 2wd utility box had a 292 I6 with 4.56 gears, and got 10 mpg. With 4.56 gears it wasn't gutless, but it was SLOW. 55 was redline and screaming.

 

For a few more miles out of a gallon of gas.
This is something most don't get any thoughts about.

All the vehicles produced in or for the US are setup with correct carb jetting so you can drive of haul/tow across the US with what was standard equipment like carb jetting per the Weight vehicles engines cu-in and so on. Now if you only stay like lets say around sea level areas then chances are you can reduce the jet size by 2-3 sizes smaller for a little better mileage. On a stock motor that is..
orich