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Afternoon all,
Just finished up a 1974 F-250 4x4, 4 speed with new FE 390 engine.
Was converted to welding truck from new and box sold, only has 47,000 miles on chassis.
Looking for opinions on what to do for better highway driving this old girl.
It has dana 4:10 gearing.
Am i better off to change gearing in diff's or go to newer 5 speed tranny?
Going to use it for hauling ATV's and sleds, and pulling a trailer.
Last edited by Flatlander56; Yesterday at 07:06 PM.
Reason: adding Marti report
What size tires are you running? 33's, 35's... Awesome looking truck!! IME w/V8/NP435 (or any 4sp manual) 4.10's and 35's are best all around gears, 33's will get you a bit more "pep" but at the sacrifice of (s)miles per gal. My 77 F250 351Measly/NP435 and 33's for the most part avgs 10, when I had 35's on him, he could still spin them when wanted, but he wasn't as thirsty, just not by much.
The cost and expense of re-gearing or swapping trans IMHO just isn't worth it, you may have different ideas, but if you keep it around 55-60 you'll have your best results and just throw the $$ in the tank, these are bricks, and as much as you want too, it's still a brick. Best mileage out of my old Ford's is my 66 F100 @ 55-60 and he has a small 300/T18/3.70's, a V8 is just going to drink the dino juice, regardless of everything else.
It won't ever pay for itself in fuel savings, but if you want to turn your 4 speed into a 7 speed overdrive put a Gearvendor in it. I did it on my '76 high boy and I'd do it again.
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