gear ratio question
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Senior User
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From: Northern Virginia
gear ratio question
I have a 65 250 with 4:10 gears and I'm thinking about changing the gears in it.The motor is very strong and the c-6 has been rebuilt recently.I am concerned about how high she revs at highway speeds.What would be a good ratio for my truck?
Joe
Joe
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Joined: Jul 2003
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From: East Central Florida
3.73:1 but not much lower than 3.50:1, unless you install an RV or other low end High torque output cam to compensate.
If you "work" it by hauling or towing stuff maybe even a 3.93:1 coupled with slightly larger diameter tires.
FBp
If you "work" it by hauling or towing stuff maybe even a 3.93:1 coupled with slightly larger diameter tires.
FBp
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Joined: Apr 2002
Posts: 3,613
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From: Coal country
Joe: Look closely at the cost of changing those gears you have a Dana, not a Ford 9".
Changing the ratio will raise your gas mileage a little bit, but will decrease your hauling performance a lot. If you don't haul anything, then performance won't a problem.
Your Dana gear options are not as varied as the Ford 9", either.
It will take a long time to recoup the savings in gas.
If you really want to change them and you don't really use it as a 250, then you might want to consider buying a 5-lug F-100 with power steering and power disc brakes and a Ford 9" rear.
You can change out the front discs to 5 lug, change the rear axle to Ford 9'' for more gear choices, and get 5 lugs all the way around.
It wll probably be as cheap in the long run.
Just a thought!
Changing the ratio will raise your gas mileage a little bit, but will decrease your hauling performance a lot. If you don't haul anything, then performance won't a problem.
Your Dana gear options are not as varied as the Ford 9", either.
It will take a long time to recoup the savings in gas.
If you really want to change them and you don't really use it as a 250, then you might want to consider buying a 5-lug F-100 with power steering and power disc brakes and a Ford 9" rear.
You can change out the front discs to 5 lug, change the rear axle to Ford 9'' for more gear choices, and get 5 lugs all the way around.
It wll probably be as cheap in the long run.
Just a thought!
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Joined: Mar 2003
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From: Long Island
i had 4.56's and my engine was screaming just to keep up in the granny lane. i swapped them out for 3.73 and now i can ride in the left lane while my engine screams. i wanted to go to a lower gear numerically, but i will be using my truck to tow. it cost me $800 to have it done. i wanted some kind of limited slip put in, but that was going to double the price, atleast.
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Senior User
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From: Northern Virginia
So far so good.I just finished with the power disc brake/Saginaw P/S swap and I like the heavy duty stuff under the truck so a 5 lug swap in not in my future(anyone want to buy a bendix P/S set up for a FE motor?).I will be hauling a 17' aluminium jet outdrive boat from time to time but my concern is running the old 390 at 3500 RPM's for a few hour trip up the road.It does on occasion get used for hauling heavy stuff to the dump and firewood and John is correct it is a dana rear,limited slip or posi or whatever they call it.It has 16.5 tires on it now.
Joe
Joe
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Joined: Nov 2006
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From: Simi Valley, CA
My truck: 1965 F100 with 390 built from original 352. 4V with RV cam. Transmission T-85 stick and overdrive. The original rear end ratio was 3.73. When I restored the truck 20 years ago, I switched to a 3.00-1 ratio because truck is just used for pleasure.
I only checked the hwy mileage a couple of times..once from Phoenix to LA, it got 28MPG...not too shabby.
I purchased this truck new in March '65, traded it in 1968 on a new F250, then bought it back as a basket case in 1981.
I only checked the hwy mileage a couple of times..once from Phoenix to LA, it got 28MPG...not too shabby.
I purchased this truck new in March '65, traded it in 1968 on a new F250, then bought it back as a basket case in 1981.
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