rear diff options
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Junior User
Joined: Aug 2006
Posts: 77
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From: hatboro pa
rear diff options
i have a 53 f250 with a 4.86 gear,i would like to know if i can bolt in a later modle f250rear diff with a lower gear ratio-with liitle or no modifications,what years can i use with little or no modifications?? a 3.73 ratio would be ideal
Posting Guru
Joined: Jun 1999
Posts: 2,415
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From: Comox Valley, Canada
Here is one link... I think there is another under Tech Articles top of page.
https://www.ford-trucks.com/article/...Lowering_.html
https://www.ford-trucks.com/article/...Lowering_.html
Posting Guru
Joined: Jun 1999
Posts: 2,415
Likes: 3
From: Comox Valley, Canada
OK wouldn't the same year F250 rears fit in????? The F100's and F250's as far as I know have the same track width .......just a different rear... usually a Dana 60 for the F250's. So I would guess you would need a pre-73 F250 rear end for the same width........or use a post-73 with a different offset on the wheel to achieve the same width. But that is just a guess........hopefully someone will be along to confirm or at least straighten this out.
Senior User
Joined: Apr 2001
Posts: 251
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From: Kentucky
A '73 or earlier Dana 60 will fit, though an axle like the one (a '72) I just got will need to have the welded on shock mounts removed since our trucks already have the mounts on the axle clamps. At least, I plan to remove the ones on my axle! 
I take it you're tired of a 50mph cruising speed and lousy fuel mileage too?
I take it you're tired of a 50mph cruising speed and lousy fuel mileage too?
Senior User
Joined: Jul 2004
Posts: 216
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From: North Branch, MI
I had the same problem, swapped in an axle out of a 69 F-250 (3.73). It took about 2 hours to do the swap. Of course that did not count the time it took to do a brake job, have the drums turned etc. The drive shaft fit with out adjustment but does not have as much play on the front shaft as it originally did but I haven't had any problems. It sure has made a difference in the driveability of the old truck. Working on the front fender replacement now and then I think it will be an S-10 T-5 to get a little better gas mileage.
Have a great day....
Bob G
Have a great day....
Bob G
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Senior User
Joined: Apr 2001
Posts: 251
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From: Kentucky
Originally Posted by sgtrwg
I had the same problem, swapped in an axle out of a 69 F-250 (3.73). It took about 2 hours to do the swap. Of course that did not count the time it took to do a brake job, have the drums turned etc. The drive shaft fit with out adjustment but does not have as much play on the front shaft as it originally did but I haven't had any problems. It sure has made a difference in the driveability of the old truck. Working on the front fender replacement now and then I think it will be an S-10 T-5 to get a little better gas mileage.
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Senior User
Joined: Jul 2004
Posts: 216
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From: North Branch, MI
Originally Posted by grover
A question for you: What did you do to correct the speedometer? I'm trying to figure out where I can get the correct speedometer gear.
For now I use a calculator program I found here on the forum somewhere and with the diameter of the tires and rear end ratio I worked out rpms for 25, 35, 45, etc and use a tach. This has worked out so far, when I do make the trans swap I'll have to work on the speed-o gear then.
I wish I could find the calculator, I thought I saved it to my hard drive if I did I didn't name it something that I could recognize.
If I find it I'll post it or at least a link to it.
Have a great day!!
Bob G
Senior User
Joined: Jul 2004
Posts: 216
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From: North Branch, MI
I found the page here on the forum it's at:
https://www.ford-trucks.com/calculat...mph_rpm/a-mph/
You can plug in the rpm, tire diameter and rear end ratio and it will calculate the speed for you.
Bob G
https://www.ford-trucks.com/calculat...mph_rpm/a-mph/
You can plug in the rpm, tire diameter and rear end ratio and it will calculate the speed for you.
Bob G