Taller gear question.
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Junior User
Joined: Jun 2004
Posts: 68
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From: Near Dallas, Texas
Taller gear question.
Well, I'm thinking that the 3.70 rear end in my 57 F100 may be a bit low for my style of driving (vertually all highway), and perhaps something around a 3.00 (or maybe higer) would help fuel milage and still not make it to big of a wuss.
Unless I put my foot in it, the AOD trans is in 3rd gear within 50 feet and in OD by 35 mph.
I'm going to a swapmeet next weekend to look for a replacement, and I really need to know 2 things;
1st - Are the axles in a 57 F100 28 or 31 spline?
2nd - What years 3rd members will DIRECTLY interchange with mine, without having to swap axles, etc..
OK, 3 things ....
If I have to search for it in my local wrecking ward, which truck/engine combinations would most likely have a gear like what I need.
Thanks guys for your input.
Unless I put my foot in it, the AOD trans is in 3rd gear within 50 feet and in OD by 35 mph.
I'm going to a swapmeet next weekend to look for a replacement, and I really need to know 2 things;
1st - Are the axles in a 57 F100 28 or 31 spline?
2nd - What years 3rd members will DIRECTLY interchange with mine, without having to swap axles, etc..
OK, 3 things ....
If I have to search for it in my local wrecking ward, which truck/engine combinations would most likely have a gear like what I need.
Thanks guys for your input.
Last edited by blue57; Jul 24, 2007 at 11:08 AM.
Elder User
Joined: Jun 2004
Posts: 800
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From: Edmonton, Alberta Canada
1) unless someone swapped rear-ends or parts, your 57 willhave 28 spline axles
2) any Ford 9" carrier (or pumpkin or whatever you want to call it) wit 28 spline axles will interchange directly. Car, truck (as long as it is not a 8-3/4" ring gear).
3) most likely candidates are most cars from 60's and 70's will have lower gear ratio and 28 spline axles and mid 70' pickups with 300 6 cyl will more than likely have the low gear ratio and 28 spline axles. most v-8 trucks from the mid 70's had 31 spline axles that i have seen.
do a search on the web for axle codes as ford from what i have seen has used the same axle codes for years to determine axle ratio (but the code does not state if it is 28 or 31 spline axles).
good luck
Rgds
Mike
2) any Ford 9" carrier (or pumpkin or whatever you want to call it) wit 28 spline axles will interchange directly. Car, truck (as long as it is not a 8-3/4" ring gear).
3) most likely candidates are most cars from 60's and 70's will have lower gear ratio and 28 spline axles and mid 70' pickups with 300 6 cyl will more than likely have the low gear ratio and 28 spline axles. most v-8 trucks from the mid 70's had 31 spline axles that i have seen.
do a search on the web for axle codes as ford from what i have seen has used the same axle codes for years to determine axle ratio (but the code does not state if it is 28 or 31 spline axles).
good luck
Rgds
Mike
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From: Kansas City area
Personally, I wouldn't go any lower than a 3:50 with an OD transmission. Depending on your tire diameter you should only turn 2000-2500 RPM at 65-70 mph. Several of the late model SUV's use a 3:70 gear with the OD. Just my opinion, so it's value is what you paid to get it. 
Fleet Owner
Joined: Jul 2004
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From: NM
Originally Posted by Jag Red 54
I would just pull an axle and count the splines to be sure. With your AOD, I would think 3.25 pinion gears would be just right. Good luck, Jag
I've been running the numbers on my '52. I have a 3.50 9" to replace the 3.92, but that is really not a huge change ( 11%). I may shop for a 3.25 (almost 20%).
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Junior User
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From: Near Dallas, Texas
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Roast em' if you got 'em
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From: Rio Rancho, NM
Originally Posted by ALBUQ F-1
Don't even need to do that. Look at the end of the axle. A "D"-shaped indent on the center is a 28-spline, two smaller holes = 31 spline. These are forged into the end, not small stamps.
I've been running the numbers on my '52. I have a 3.50 9" to replace the 3.92, but that is really not a huge change ( 11%). I may shop for a 3.25 (almost 20%).
I've been running the numbers on my '52. I have a 3.50 9" to replace the 3.92, but that is really not a huge change ( 11%). I may shop for a 3.25 (almost 20%).
When I was looking into the axle thing I read about that method of identification. Don't rely on it. From what I have read it mainly applies to Ford cars starting somewhere in the late 60's. My 1960 9" has the 2 smaller holes but I'm pretty sure they didn't even start making the 31 spline diff until the mid 60's (at least thats what I think I remember what NumberDummy told me)
Here's a decent article on 9" fords;
http://www.kevinstang.com/Ninecase.htm
There's alot of info on the net about 9" diffs and axles and it all gets very confusing very quick (maybe thats why I've been putting off finding a replacement for my 4:11's)
Good luck
Bobby
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From: Ottawa, Ontario
Originally Posted by blue57
Unless I put my foot in it, the AOD trans is in 3rd gear within 50 feet and in OD by 35 mph.
Roast em' if you got 'em
Joined: Mar 2005
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From: Rio Rancho, NM
Here's soem more reading on 9" Fords from a previous post. It looks like the 31 spline diffs weren't offered until 1968
https://www.ford-trucks.com/forums/6...ghlight=9+ford
Good luck
Bobby
https://www.ford-trucks.com/forums/6...ghlight=9+ford
Good luck
Bobby
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From: Littleton, New Hampshire
Originally Posted by LEckart
Personally, I wouldn't go any lower than a 3:50 with an OD transmission. Depending on your tire diameter you should only turn 2000-2500 RPM at 65-70 mph. Several of the late model SUV's use a 3:70 gear with the OD. Just my opinion, so it's value is what you paid to get it.
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From: Rockford, IL
Originally Posted by Conanski
Your TV cable is set too loose, tighten it up a click or two and the shift points will get higher.
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From: Kansas City area
blue57
Here's a link to a site to calculate your rpm for whatever rear gear and tire size. I imagine your OD drive is in the area of 0.70. http://golenengineservice.com/calc/calcrpm.htm
Here's a link to a site to calculate your rpm for whatever rear gear and tire size. I imagine your OD drive is in the area of 0.70. http://golenengineservice.com/calc/calcrpm.htm
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i have 2.75 gears in my 60 panel. with 215 75 15 in the rear. ford 400 with a holley economaster carb edlebrock intake and c6 tranny. I can peel out like nobodys buisness. Plus I am turning 2500 at about 73 - 75 mph on the highway. I s**t you not I am getting 24 miles to the gallon witht he truck empty and with all my biz stuff I get 21.3 I love it and am not gonna trade for anything else! I do not know what I get in town have not caulated that. but I have a moblie biz and so I have done a lot of highway drivin to and from lA and San Jose area. I live by fresno. so i am getting that consitantly if that is worth anythng there ya go. oh yeah I got mine out of a ford truck actually I am not sure what year I got it at a truck wrecking yard. and it turned out to be posi. at least I think it is I can peel out i lay two patches of rubber not one. so I am not sure, because if you spin one the other spins the other direction????