I have used the 302 engine and 4 speed automatic transmission from a 91 F150 in my 1964 F100. The original differential ratio is 3:56. Did the F150 come with a lower ratio than 3:56? As I am looking for better fuel milage not hauling power.

 

Are you sure it was 3:56 and not 3:55? From what I know you can get the 3:08 gear ratio from some of the newer trucks. Don't know about the '64 models. Oldest I have is '71.

With the 302 you may not have the power to turn those gears and improve your mileage. I may be wrong. Hopefully Conanski will check this and correct me if I am wrong.

 

I don't want to come off as a wise **** but you're terminology isn't right. What you are looking for is actually a higher ratio. The larger the number the lower the gear ratio. Lower ratios are best when you need a lot of pulling power. Higher ratios are best for fuel economy but you sacrifice some low end power.

In answer to your question yes the later trucks did come with some higher ratios. Jarod17 is correct on the 3.08's. My 96 F150 has them. If your 64 still has the original rear then it is most likely a 9" Ford unit. If so you have lots of choices. The only other rear Ford used in F100s was a Dana 44. There weren't nearly as many 44's as 9" rears. The 9" rears were used in cars and trucks from the late 50's into the early 80"s. There are lots of gear sets available both used O.E.M. and aftermarket.

My 72 F100 has a mild 289, C4 combo with 3.25's. It has enough power to run with traffic but still gets decent mileage.

 

Thanks for correcting me on the higher and lower I should have known that and the ratio.
The reason for asking the question is because the trucks original diff. is a posi traction Dana 60 with a set of 4:10 gears and before you say it can't be, I have done extensive research, it is. I can get a set of 3.55 installed into the Dana 60 for about $500. which would match the 91 302 and 4 speed automative drive train.
I have a line on a Ford 9" with unknown ratio and no posi.. I figure by the time I get the housing, new gears, new posi., bearing and new drive shaft. The Dana 60 have a longer pinion shaft by about 2 1/2". It will set me back about $1200. to $1500. Will it really be worth the added expense, this will be a daily drive eventually.
Your Thoughts

 

Are you running stock tires or oversized tires? If you are going for better mileage I would run stock tires and go with the 3:55 gears.

 

I wouldn't say it can't be the original rear under an F100. I never seen a D60 equipped F100 but a friend of mine did. I've heard of a couple others.If you can get the 60 regeared for $500 I'd say go for it. For a daily driver it wouldn't be worth the money to swap it.

 

Correct me if I'm wrong, but you have a 64 f100 with the engine & trans from a 94ish f-150?
I have recently undergone the pain of the Dana 60-2(1/2 ton dana 60 used in early 60's f-100 limited slip applications), & just completed a swap to a 9".

I have the y block still in mine, however I thought that using the big dana 60 would be unique & bullet proof way of going.
I now have over 1500.00 into the dana 60-2, & couldn't afford to drive the truck due to the 4.10 gears. I found a 66 f100 9" & completed the swap for under 350.00, & also found a 74 9" pumkin with 3.00:1 gears & a rebuilt factory track lock to boot!
My lil' y block still pulls just fine, & is a pleasure to drive on the highway.
The nice thing is, that when I update the truck with either an overdrive tranny, or a different motor build, etc. I can pull the gears with ease & not have the headache involved with gear setup on the dana.

The biggest problems that I encountered were that the Dana 60-2 is so rare that parts are difficult to come by. I ended up with a broken axle, & none could be found anywhere in salvage. I ended up having to have one built.

Ford 9" from 60-66 are all the same width. 66, & possibly 65 have slightly diffent shock mounts as I am learning, but not the end of the world.

My two cents,
Regards

 

Yes, I finished the truck this summer.
A fuel injected 302 and 4 speed automatic 91 F150, single piece drive shaft as the transmission is only 2" away from where the center hanger should be.
I am running the 91 rims and tires.
I understand the advantage of the 9" but my concern finding the one that I am looking for with the posi. and the correct gear that doesn't need a ton of money poured into it. This truck right now will not spin the wheels even on wet pavement, with the 4:10 gears, which is why I am sticking with the posi.
Thanks Still not sure.