What gears to use
Freshman User
Joined: Nov 2004
Posts: 25
Likes: 0
It depends on the size tire you have .
Heres a rule of thumb :
30" or smaller = 3.54's
31"-33" = 3.73's
34-36's = 4.10's or 4.56's
Over 36's " = 4.56 - 5.12's
These are just estimates for good power and still have some good highway .
Heres a rule of thumb :
30" or smaller = 3.54's
31"-33" = 3.73's
34-36's = 4.10's or 4.56's
Over 36's " = 4.56 - 5.12's
These are just estimates for good power and still have some good highway .
Senior User
Joined: Sep 2003
Posts: 238
Likes: 0
From: Bridgeville,CA
Like 69svtf100 said, it is up to ypu. The higher the number the "more power" you will have at the rear wheels and the worse your mileage will be. The lower the number you have will give you less power and better mileage. It all ties into the tire size too as he said. Unless you have a overdrive transmission everything is straight thru in high gear so the only real variable is the gear ratio.
Fleet Owner
Joined: Jun 1999
Posts: 24,552
Likes: 74
From: Creedmoor, North Carolina
Mark, Another thought for your rear numbers. You would use a high number like the one suggested with a small motor. The larger the motor the lower the number.
You are talking about getting power to the ground, and a lot of factors can go into the planning. Should you use a big motor like a 390 and 3.73 you will have gobs of power and low mpgs. With you having a 4x4 you need twice the planning.
a couple o coppers
John
You are talking about getting power to the ground, and a lot of factors can go into the planning. Should you use a big motor like a 390 and 3.73 you will have gobs of power and low mpgs. With you having a 4x4 you need twice the planning.
a couple o coppers
John
Elder User
Joined: Jul 2004
Posts: 920
Likes: 0
From: Westminster, Colorado
Can any of you guys teel me which gears I have bassed on this.....I currently have 33" tires all around and I notice that my Speedo reads 6/5's of the actual speed....that is, 25MPH reads as 30 and 55MPH reads as 66. Can we determine which gears I have based on this?
Lead Driver
Joined: Apr 2001
Posts: 6,175
Likes: 21
From: Texas
Originally Posted by Unimog005
Can any of you guys teel me which gears I have bassed on this.....I currently have 33" tires all around and I notice that my Speedo reads 6/5's of the actual speed....that is, 25MPH reads as 30 and 55MPH reads as 66. Can we determine which gears I have based on this?
we might be able to make a guess with those numbers. But, we really need some tach readings.
The 33s will have approximately the same effect on your speedo regardless with what gear set you have...
Trending Topics
Elder User
Joined: Jul 2004
Posts: 920
Likes: 0
From: Westminster, Colorado
I would have to say that 60 to 65MPH (actual speed) puts me right around 3000RPM. It is a 390 Engine with a NP435 and np205 T-fer case.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Top 10 Ford Truck Tragedies
Joe Kucinski
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
Senior User
Joined: Jul 2003
Posts: 106
Likes: 0
Smaller gears will only improve your Fuel economy to a certain point. When you go too small your engine runs below its optimum power range, and it will accelerate like crap and be a dog when hauling, But you can get away with smaller gears if you use the granny gear sometimes, Only sucks beacuse first isnt synchronized. 69svtf100 has got the right idea, Also consider if you do a lot a city or highway driving. I Do almost all city have 235/75/15(stock) and 3.7's and get 15-16mpg maby 17 if i took it easy on the pedal and didnt have to idle to warm up in the morning being winter and a broken choke.
Lead Driver
Joined: Apr 2001
Posts: 6,175
Likes: 21
From: Texas
Originally Posted by Unimog005
I would have to say that 60 to 65MPH (actual speed) puts me right around 3000RPM. It is a 390 Engine with a NP435 and np205 T-fer case.
Sounds like 4.10s to me. That's where mine runs at 60-65mph, 3000rpm. I run 4.10 gears with 255-70r16 tires (30.1" diameter).