Regearing questions
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Laughing Gas
Joined: Jun 2010
Posts: 1,056
Likes: 10
From: Indiana, PA
Regearing questions
My truck is a 1976 F.250 4x4 with 4.10 gears in it currently and 36in. tall tires. I was thinking about re-gearing the axles in it to 3.54 or maybe even 3.08. My issue is that to just go 55mph I am spinning 2500 r.p.m. in 4th gear and would like to lower that number to about 1800 or so. Anyone else do this or have any recommendations. Also would 3.08`s be too extreme?
Lead Driver
Joined: Mar 2004
Posts: 8,922
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Yes 308 would be too much, even with 3.54's you are going to loose a lot of power. If you are looking for gas milage, unless you drive highways all the time I wouldn't bother unless you have axles to bolt in that already have the gears in them. It's a lot of work to regear from scratch and it won't be cheep either.
Fleet Mechanic
Joined: May 2012
Posts: 1,724
Likes: 1
From: peru kansas
650 if your calculations are correct with 36's and 4.10 gears 2500 rpm would be 65.25 mph sounds to me like you have 4.56 gears(same 36's and 2500 rpm is 58.65 mph)............3.54 gears will give you 54.41 mph at 1800 rpm and your 36's..... i hope this helps you make your choice's........ (basic math equation.... rpm / gear ratio x tire distance traveled in inches / 12 / 5280 x60 = rpm vs gears) i hope this helps 
Elder User
Joined: Oct 2011
Posts: 605
Likes: 1
From: Castle Rock, CO
Hi 650-timely posting for me. I too am debating between a gear change and/or an overdrive or gear splitter. I have a 2WD, 460 w/C6 and 4.10. I was thinking of changing to a 3.73, so I still have adequate power, AND may consider adding the Gear Vendor OD unit. I can't seem to find an auto tranny w/OD to replace the C6 that will bolt on. Not cheap but I'll be happier in the long run so maybe it will be worth it.
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Laughing Gas
Joined: Jun 2010
Posts: 1,056
Likes: 10
From: Indiana, PA
Yes 308 would be too much, even with 3.54's you are going to loose a lot of power. If you are looking for gas milage, unless you drive highways all the time I wouldn't bother unless you have axles to bolt in that already have the gears in them. It's a lot of work to regear from scratch and it won't be cheep either.
650 if your calculations are correct with 36's and 4.10 gears 2500 rpm would be 65.25 mph sounds to me like you have 4.56 gears(same 36's and 2500 rpm is 58.65 mph)............3.54 gears will give you 54.41 mph at 1800 rpm and your 36's..... i hope this helps you make your choice's........ (basic math equation.... rpm / gear ratio x tire distance traveled in inches / 12 / 5280 x60 = rpm vs gears) i hope this helps
I`d love to have a 5spd nv4500. My issue is I`d have to go buy a $300 adapter plate and then try to find a used tranny somewhere and everywhere I look people think the nv4500 trannys are pure gold even if they have 250,000 on them and need a full rebuild, they still want $400 at least.
Heres a perfect article on how to do it for anyone interested. Installing the NV4500 Overdrive Transmission .: Articles
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Postmaster
Joined: Nov 2011
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650 if your calculations are correct with 36's and 4.10 gears 2500 rpm would be 65.25 mph sounds to me like you have 4.56 gears(same 36's and 2500 rpm is 58.65 mph)............3.54 gears will give you 54.41 mph at 1800 rpm and your 36's..... i hope this helps you make your choice's........ (basic math equation.... rpm / gear ratio x tire distance traveled in inches / 12 / 5280 x60 = rpm vs gears) i hope this helps
Logistics Pro
Joined: Feb 2011
Posts: 3,522
Likes: 11
From: Townsend, MT
Clark made an over drive 5 speed that was sometimes used behind FT's. The FT bellhousing is 7 7/16" while your bellhousing is 6 13/16". The only problem is, OD clarks seem to be like hen's teeth.
Post Fiend
Joined: Apr 2008
Posts: 8,261
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From: Big Sky Country
35's or 36's play pretty well with the 4.10 gearing, @55-65mph they keep the motor right in its powerband.
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