need help with differential
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Joined: Apr 2003
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need help with differential
i have a 1960 f100 that i have been working on for the last year or so. i put a new 289 in it, as that was what it had when i got it, and it has a 3 speed tranny and it hauls ***. my problem is that when i jump on the freeway, the rpms jump way up and it cruises at about 4250rpm. i was given advice to re-gear the rear end, but i have no idea what size gear is in it or what size gear to put in it. my neighbor says he can help put the gear in, but cannot tell what size gear is in it. any help would be appreciated.
Senior User
Joined: Aug 2003
Posts: 103
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From: Poplar-Point Manitoba
start by looking for the ID tag on the truck(where the vin is).It should state things like the body style,color,and axle ratio(if original).
Running that high rpm's on the highway,either you have a really deep gear set(4.60:1),or you actually have a 4 speed and can't get it into high gear!!
The only other way to tell is to take it apart and count the teeth...the method of turning one wheel and counting driveshaft turns has never worked for me.
To get highway rpm's down,either get about a 3.25:1 gearset, or, an overdrive trans.
Hope this helps
Graham
Running that high rpm's on the highway,either you have a really deep gear set(4.60:1),or you actually have a 4 speed and can't get it into high gear!!
The only other way to tell is to take it apart and count the teeth...the method of turning one wheel and counting driveshaft turns has never worked for me.
To get highway rpm's down,either get about a 3.25:1 gearset, or, an overdrive trans.
Hope this helps
Graham
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Joined: Nov 2000
Posts: 11,591
Likes: 14
From: Pflugerville, tx
Hm.. I was able to get the gear ratio on my sons pickup by using the wheel/driveshaft approach
jack up one side of the rear axle, make sure the other still touches the ground. Use some chalk or tape to mark a spot on the tire, same for the driveshaft at the rear axle.
Have someone turn the wheel slowly 10 revolutions, and count the number of times the driveshaft truns, divide by 10.
so you might get a little more than 41 turns of the driveshaft for the 10 turns of the tire, and that would be 4.1(1), or 45 1/2 for 10 and that would be 4.5(6)
Sam
jack up one side of the rear axle, make sure the other still touches the ground. Use some chalk or tape to mark a spot on the tire, same for the driveshaft at the rear axle.
Have someone turn the wheel slowly 10 revolutions, and count the number of times the driveshaft truns, divide by 10.
so you might get a little more than 41 turns of the driveshaft for the 10 turns of the tire, and that would be 4.1(1), or 45 1/2 for 10 and that would be 4.5(6)
Sam
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Joined: Mar 2004
Posts: 220
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From: north central illinois
scoobzter
i recently blew the spiders out of my 58 f100's original 9" rear end. the axles, 28 spline, the third member, ring and pinion where good just the spiders where junk so you could get a locker or another open carrier for it. or just use the gears and your carrier. it is a 3.20 gear in the rear end. on 26" tall tires you will cruize at 2250 rpm or so. if all fails in your attempt to figure out what gear you have you can always pull hte third member out and count the ring and pinion. if you are interested in there let me know i'll work something out with you.
i recently blew the spiders out of my 58 f100's original 9" rear end. the axles, 28 spline, the third member, ring and pinion where good just the spiders where junk so you could get a locker or another open carrier for it. or just use the gears and your carrier. it is a 3.20 gear in the rear end. on 26" tall tires you will cruize at 2250 rpm or so. if all fails in your attempt to figure out what gear you have you can always pull hte third member out and count the ring and pinion. if you are interested in there let me know i'll work something out with you.
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