Advice on gear ratio swap please
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Cross-Country
Joined: Jun 2003
Posts: 51
Likes: 3
Advice on gear ratio swap please
First of all, thanks for taking time to read and hopefully respond to this newbie question. I have been poking around the various sites looking for a mid 50's F100. I have found a prospect not too far away. A 1955 with a replacement 292 V8, three speed manual. The owner isn't sure about gears, but I suspect it still has the 3.92 rear and as far as I can figure, RPM at highway speeds is going to be higher than optimal. I figure about 2885 at 60 MPH and 3365 at 70 MPH. I am looking for a set up that will offer lower RPM for those times I have to be on the main roads. I don't mind the three speed manual but I could live with an automatic with OD as well. Can someone who has addressed this problem offer some advice? I confess I will have to hire this work done so it would be a good idea for me to know what I want before going ahead with any purchase and trying to find somebody to make the change for me. Thanks again and I apologize if this topic been beaten to death before.
John
John
Mountain Pass
Joined: Dec 2021
Posts: 102
Likes: 38
From: Central NJ
https://www.summitracing.com/newsand...tio-calculator
This should let you figure out what would be ideal for your driving style.
This should let you figure out what would be ideal for your driving style.
Laughing Gas
Joined: May 2010
Posts: 1,125
Likes: 191
From: Wharton, PA
If you do have the 3.92 gear... to go down to a 3.73 you will also have to replace the differential carrier. See link.
https://www.differentials.com/techni...arrier-breaks/
https://www.differentials.com/techni...arrier-breaks/
Lead Driver
Joined: Nov 2002
Posts: 9,680
Likes: 1,251
From: Jefferson City, MO
Verify your gear first just to make sure.
If you have to replace the differential carrier, it might be cheaper to get a whole new rear for the truck. That is what I ended up doing for my truck.
I like to keep things stock so I kept mine a Dana 60 (I have an F250). If you stay with your Dana 44, which is easier, you would need to find something 1972 or older due to width.
If you want to change completely.....well there are lots of options. It just depends on what you want to spend. I'm cheap in addition to liking to stay fairly stock.
If you have to replace the differential carrier, it might be cheaper to get a whole new rear for the truck. That is what I ended up doing for my truck.
I like to keep things stock so I kept mine a Dana 60 (I have an F250). If you stay with your Dana 44, which is easier, you would need to find something 1972 or older due to width.
If you want to change completely.....well there are lots of options. It just depends on what you want to spend. I'm cheap in addition to liking to stay fairly stock.
Thread Starter
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Cross-Country
Joined: Jun 2003
Posts: 51
Likes: 3
Originally Posted by Harrier;[url=tel:20474824
20474824[/url]]Verify your gear first just to make sure.
If you have to replace the differential carrier, it might be cheaper to get a whole new rear for the truck. That is what I ended up doing for my truck.
I like to keep things stock so I kept mine a Dana 60 (I have an F250). If you stay with your Dana 44, which is easier, you would need to find something 1972 or older due to width.
If you want to change completely.....well there are lots of options. It just depends on what you want to spend. I'm cheap in addition to liking to stay fairly stock.
If you have to replace the differential carrier, it might be cheaper to get a whole new rear for the truck. That is what I ended up doing for my truck.
I like to keep things stock so I kept mine a Dana 60 (I have an F250). If you stay with your Dana 44, which is easier, you would need to find something 1972 or older due to width.
If you want to change completely.....well there are lots of options. It just depends on what you want to spend. I'm cheap in addition to liking to stay fairly stock.
Lead Driver
Joined: Oct 1999
Posts: 6,776
Likes: 553
From: Kalispell, MT
57-72 9" is another option with lots of gear choices.
I like 3.50 gears and highway speeds are easy at around 2500 rpm with 16" wheels.
I like 3.50 gears and highway speeds are easy at around 2500 rpm with 16" wheels.
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Cross-Country
Joined: Jun 2003
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Originally Posted by mtflat;[url=tel:20474920
20474920[/url]]57-72 9" is another option with lots of gear choices.
I like 3.50 gears and highway speeds are easy at around 2500 rpm with 16" wheels.
I like 3.50 gears and highway speeds are easy at around 2500 rpm with 16" wheels.
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Laughing Gas
Joined: Sep 2008
Posts: 966
Likes: 27
From: Missouri
Verify your gear first just to make sure.
If you have to replace the differential carrier, it might be cheaper to get a whole new rear for the truck. That is what I ended up doing for my truck.
I like to keep things stock so I kept mine a Dana 60 (I have an F250). If you stay with your Dana 44, which is easier, you would need to find something 1972 or older due to width.
If you want to change completely.....well there are lots of options. It just depends on what you want to spend. I'm cheap in addition to liking to stay fairly stock.
If you have to replace the differential carrier, it might be cheaper to get a whole new rear for the truck. That is what I ended up doing for my truck.
I like to keep things stock so I kept mine a Dana 60 (I have an F250). If you stay with your Dana 44, which is easier, you would need to find something 1972 or older due to width.
If you want to change completely.....well there are lots of options. It just depends on what you want to spend. I'm cheap in addition to liking to stay fairly stock.
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Cross-Country
Joined: Jun 2003
Posts: 51
Likes: 3
The only reason the limited slip might an issue is that my garage sits on a slope above the driveway and the grassy area leading to it can be slick. I'm guessing this might be a problem, especially in the case of a truck with a fairly light rear end. The 68 GTO with Saf-T-Ttrack limited slip climbs up there just fine. So for now it seems I have a few options, replace just the differential carrier, replace with a whole new rear which would include changing the carrier to accommodate different gears, go with a Ford 9 using a 57-72 F100 set up or one of the various others I found on another post...Or investigate a Tremec 5 speed or automatic transmission with OD. Like Harrier said, it's all up to how much a guy wants to spend.
Last edited by johnnyv; Jul 11, 2022 at 09:12 PM. Reason: addition to original
Hotshot
Joined: Oct 2009
Posts: 16,174
Likes: 4,781
From: Burbank, WA
Changing the rear end is going to be far less expensive and work than swapping the trans. Lots of options from changing the Dana carrier to a limited slip carrier and 3.50 (my choice if I'm going to the trouble to swap ratios) gears, to finding a 9" or even an Explorer rear. Those come factory commonly with a limited slip diff.
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