Rear End Ratios
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Captain
Joined: Jun 2007
Posts: 687
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From: Calgary
Rear End Ratios
Heya..
Okay, so I've owned my truck almost a year. I understand that a 4.10 rear end requires more RPM for similar road speed as a 3.73. The 3.73 gives better fuel mileage unless you are towing heavy loads from what I've been told.
I do notice however that people change between 4.10 and 4:10. Which is correct?
I would assume that 4.10:1 means the engine turns over 4.10 for every 1 of the rear axel with no reduction in the tranny.
4:10 would mean 4 turns of the engine (or axel) would result from 10 turns of the axel, or engine with no reduction in the tranny.
Which is correct, or am I missing the ballpark?
Okay, so I've owned my truck almost a year. I understand that a 4.10 rear end requires more RPM for similar road speed as a 3.73. The 3.73 gives better fuel mileage unless you are towing heavy loads from what I've been told.
I do notice however that people change between 4.10 and 4:10. Which is correct?
I would assume that 4.10:1 means the engine turns over 4.10 for every 1 of the rear axel with no reduction in the tranny.
4:10 would mean 4 turns of the engine (or axel) would result from 10 turns of the axel, or engine with no reduction in the tranny.
Which is correct, or am I missing the ballpark?
Administrator
Joined: Jul 2007
Posts: 24,686
Likes: 21
From: South Georgia/East Florida
4.10 : 1 is actually correct, although the 1 is almost always assumed and not used. It is the amount of times the driveshaft spins per single tire revolution.
Although there is a general thinking that the lower the numerical gearing, the better gas mileage you will attain by virtue of your RPMs being lower at a given speed.
However, in real world driving this is often not the case. Because you turn more RPMs with less throttle, most people see a modest gain in city (stop & go) driving, while only seeing a modest loss while cruising on the highway.
It's not unheard of to gain as much as 2 mpg in city driving with as much as 4.56 gears, although you'll usually give about the same amount back at high speeds on the interstate.
Of course, when determining a re-gear, it's probably more important to consider what your EFFECTIVE GEAR RATIO would be after a gear swap...
Although there is a general thinking that the lower the numerical gearing, the better gas mileage you will attain by virtue of your RPMs being lower at a given speed.
However, in real world driving this is often not the case. Because you turn more RPMs with less throttle, most people see a modest gain in city (stop & go) driving, while only seeing a modest loss while cruising on the highway.
It's not unheard of to gain as much as 2 mpg in city driving with as much as 4.56 gears, although you'll usually give about the same amount back at high speeds on the interstate.
Of course, when determining a re-gear, it's probably more important to consider what your EFFECTIVE GEAR RATIO would be after a gear swap...
Last edited by HammerZ71; Apr 2, 2011 at 06:08 PM.
Administrator
Joined: Jul 2007
Posts: 24,686
Likes: 21
From: South Georgia/East Florida
Hell, I had my stock 3.92s sitting in a box in storage until just before x-mas, I finally got tired of moving the heavy a$$ box everytime I went in there to look for something, not to mention I coulda used some extra x-mas cash. Sold the set (front & rear) for $125 + 25 shipping...
Not to **** you off, but I played in a golf tourney today across the state and rode with the guy I partnered with in his '02 4.7 QCSB 4x2 Ram and according to the overhead got 19.3 mpg on the 155 mile round trip (mostly highway). I dunno what gears he has although I'm sure they are stock, I'll have to ask him if they are 3.55 or 3.92 if he even knows. I don't think he has a single mod and has big time soccer mom tires on it, probably about 31.5-32" on the factory 17s...
Not to **** you off, but I played in a golf tourney today across the state and rode with the guy I partnered with in his '02 4.7 QCSB 4x2 Ram and according to the overhead got 19.3 mpg on the 155 mile round trip (mostly highway). I dunno what gears he has although I'm sure they are stock, I'll have to ask him if they are 3.55 or 3.92 if he even knows. I don't think he has a single mod and has big time soccer mom tires on it, probably about 31.5-32" on the factory 17s...
Last edited by HammerZ71; Apr 17, 2011 at 08:57 PM.
Rookie
Joined: Apr 2010
Posts: 56
Likes: 0
From: Ga
Hell, I had my stock 3.92s sitting in a box in storage until just before x-mas, I finally got tired of moving the heavy a$$ box everytime I went in there to look for something, not to mention I coulda used some extra x-mas cash. Sold the set (front & rear) for $125 + 25 shipping...
Not to **** you off, but I played in a golf tourney today across the state and rode with the guy I partnered with in his '02 4.7 QCSB 4x2 Ram and according to the overhead got 19.3 mpg on the 155 mile round trip (mostly highway). I dunno what gears he has although I'm sure they are stock, I'll have to ask him if they are 3.55 or 3.92 if he even knows. I don't think he has a single mod and has big time soccer mom tires on it, probably about 31.5-32" on the factory 17s...
Not to **** you off, but I played in a golf tourney today across the state and rode with the guy I partnered with in his '02 4.7 QCSB 4x2 Ram and according to the overhead got 19.3 mpg on the 155 mile round trip (mostly highway). I dunno what gears he has although I'm sure they are stock, I'll have to ask him if they are 3.55 or 3.92 if he even knows. I don't think he has a single mod and has big time soccer mom tires on it, probably about 31.5-32" on the factory 17s...
Thats what i get hwy in my 08 4.7 with 3.92. hell i have done more on the hwy especially after the spark plug change, oil change (RP), and a few other misc.. stuff. no mods. this is of course my overhead display,which is about a half a gallon to a gallon off at times.
