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Could anyone help explain gear ratio's to me. Are some gear ratio's for towing, and others for highway driving? I have a 1972 F250 2wd with a 390 engine, C6 transmission, and a Dana 60 rear end with 4:10 gears. Are the 4:10 gear ratio for highway speed use or for some other purpose? Thanks for any help explaining this. Bruce
Could anyone help explain gear ratio's to me. Are some gear ratio's for towing, and others for highway driving? I have a 1972 F250 2wd with a 390 engine, C6 transmission, and a Dana 60 rear end with 4:10 gears. Are the 4:10 gear ratio for highway speed use or for some other purpose? Thanks for any help explaining this. Bruce
With a numerically high gear ratio, like a 4.10, the driveshaft rotates 4.1 times per one wheel revolution whereas a numerically low ratio like a 2.80 the driveshaft only turns 2.8 times for every one wheel revolution. .. the former is good for towing and hauling heavy loads and the latter is a slug off the line due to less working leverage but it will cruise at a lower RPM at the same speed.
Don't get confused with the statement "shift into a higher gear" because that refers to 3rd, 4th, or 5th gear of the transmission... not the rear axle.
... Oy... we won't even get into 'final drive ratios'.
You need a 3.54 ring and pinion to reduce cruising rpm and to decrease fuel consumption. They are scarce but not rare. You will need a pro to make the swap unless you are intimately familiar with the D60. If you can get the parts and labour for $500 you're doing ok. I made the change from a 4.56 to a 3.73, because I couldn't find a 3.54, and it made a world of difference. I could keep up with traffic on the freeway, noise went down, and the inadequacy of the brakes became very evident.
Eric
You need a 3.54 ring and pinion to reduce cruising rpm and to decrease fuel consumption. They are scarce but not rare. You will need a pro to make the swap unless you are intimately familiar with the D60. If you can get the parts and labour for $500 you're doing ok. I made the change from a 4.56 to a 3.73, because I couldn't find a 3.54, and it made a world of difference. I could keep up with traffic on the freeway, noise went down, and the inadequacy of the brakes became very evident.
Eric
that's nice to hear , I am doing 3.50's in my 9" and I am a little worried it will be too low with 33" tires, also completing a disc brake power steering setup but still worried about the low gears. I also had 4.10's
Bruce, You have a towing truck, & unlike your 9in, swapping ratios is a bit harder. That thing ought to pull like a train and suck gas out of the tank at 70mph like you have a shop vac hose in the gas tank.
Good explanation above on how the ratio numbers work. A lot of these trucks came with 4.10's factory. Not so great for the highway but will tow anything or 4 low, 1st gear and 4.10's these trucks can pull a house down. Gotta love them low gears. A gear swap to a 3.54 will give you better gas milage along with more highway speed without your engine screaming.
I had 4.56 gears in my 67 f250. I thought it was broken because it was so slow. I swapped out both axles from a 78-79 with 3.54 ratio with disc front brakes and a 4 bolt power steering mod. That entire swap was less than $500 with new pads and I rebuilt the calipers.
It is a whole different truck. Still climb a telephone pole in granny.
I will soon know how a ZF5 and 460 like the ratio.
The only way to go, discs and real power steering. I cringe when people post about rebuilding their closed knuckle axle with drums and power assist. Waste of money.