front and rear ratios
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Elder User
Joined: Jan 2008
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From: SW Washington coast
front and rear ratios
How exact a match must the front and rear gear ratios be and if there is a mismatch, which can be faster and by how much?
I have heard of having the front just a hair faster for the soft stuff ...
I have heard of having the front just a hair faster for the soft stuff ...
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From: Virginia
You usually have no choice. People think there is some "design plan" with the ratios. The factory used what was available. My 1980 had a 3.55 dana front end ratio, and a 9 inch Ford 3.50 rear. Why? Because dana's had 3.55's available, and 9 inch rears had 3.50 available.
If a certain brand "A" differential is only available in a 4.10 ratio, and brand "B" rearend is only available in a 4.11 ratio, then they will be used in the same truck, were they fit, front or rear.
Usually the tires cause more difference than anything else, even when you buy all the same at once and they get some miles on them.
The only thing to need to watch out for is don't put a 4.11 with a 3.50, or something radical like that.
If a certain brand "A" differential is only available in a 4.10 ratio, and brand "B" rearend is only available in a 4.11 ratio, then they will be used in the same truck, were they fit, front or rear.
Usually the tires cause more difference than anything else, even when you buy all the same at once and they get some miles on them.
The only thing to need to watch out for is don't put a 4.11 with a 3.50, or something radical like that.
Post Fiend
Joined: Nov 2003
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From: Nutter Fort, WV
On a 4x4 use the same size tires on both axles.
Yes you can calculated the gear ratio to tire size ratio to come up with the same driveshaft RPM number at the transfer case while running different size tires.
As an example if you had 4.10 gears in the rear axle and 3.55's in the front you could still drive it in 4x4 with the correct tires.
33" diameter tires on the front axle and 38.1" diameter tires on the rear would be close enough to run and work OK.
But you have to calculate the tire revolutions per mile and driveshaft revolutions per mile for both tire and gear combinations, then get the numbers to match with the same driveshaft revolutions per mile before you can engage the transfer case in 4x4.
38.1" tires on a 4.10 axle ratio would have a driveshaft speed of 3300 RPM and run 91.22 MPH.
33" tires on a 3.55 axle ratio would have a driveshaft speed of 3300 RPM and run 91.25 MPH.
Now the hard part is finding 33" tires and 38.1" diameter tires that stay in the same basic diameter relationship with varying loads.
Yes you can calculated the gear ratio to tire size ratio to come up with the same driveshaft RPM number at the transfer case while running different size tires.
As an example if you had 4.10 gears in the rear axle and 3.55's in the front you could still drive it in 4x4 with the correct tires.
33" diameter tires on the front axle and 38.1" diameter tires on the rear would be close enough to run and work OK.
But you have to calculate the tire revolutions per mile and driveshaft revolutions per mile for both tire and gear combinations, then get the numbers to match with the same driveshaft revolutions per mile before you can engage the transfer case in 4x4.
38.1" tires on a 4.10 axle ratio would have a driveshaft speed of 3300 RPM and run 91.22 MPH.
33" tires on a 3.55 axle ratio would have a driveshaft speed of 3300 RPM and run 91.25 MPH.
Now the hard part is finding 33" tires and 38.1" diameter tires that stay in the same basic diameter relationship with varying loads.
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Elder User
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From: SW Washington coast
I plan on keeping with a set of 4 matching tires ... So I guess staying with factory gears is ok ... I might drop the tire size down a notch tho from factory ... Looks like it will be 15's ... lol ...
Is it possible to change a c6 gear ratios? Or the primary in the t case?
Is it possible to change a c6 gear ratios? Or the primary in the t case?
Carpenter Local 745
Joined: Apr 2006
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From: on da beach
What? Use same size tires all around on a 4x4?
I know you are suppose to keep them the same on street driven rides, very wild things can happen to a truck with different size tires on the front and rear of an engaged drivetrain 4x4.
Knowing your equipment when ordering a new set of rings and pinions is a must. Being off numerically slightly is no big deal.
My point about about running smaller diameter front tires, full competition trucks do this with matched to RPM rings and pinions.
Unmatched tires would be impractical all the way around(front to back-sort a speak).
I know you are suppose to keep them the same on street driven rides, very wild things can happen to a truck with different size tires on the front and rear of an engaged drivetrain 4x4.
Knowing your equipment when ordering a new set of rings and pinions is a must. Being off numerically slightly is no big deal.
My point about about running smaller diameter front tires, full competition trucks do this with matched to RPM rings and pinions.
Unmatched tires would be impractical all the way around(front to back-sort a speak).
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From: Virginia
I plan on keeping with a set of 4 matching tires ... So I guess staying with factory gears is ok ... I might drop the tire size down a notch tho from factory ... Looks like it will be 15's ... lol ...
Is it possible to change a c6 gear ratios? Or the primary in the t case?
Is it possible to change a c6 gear ratios? Or the primary in the t case?
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From: Out of here
I remember reading somewhere a long time ago that the factory intentionally installed slightly different gear sets front and rear due to parasitic losses in the drive line.
Supposedly the front axle turns slightly slower because of all of the additional moving components as opposed to the rear.
For example: 4.10's in the rear 4.11's in the front or maybe the other way around.
I can't remember any more. It's too early to really think about it, and I need a coffee.
Supposedly the front axle turns slightly slower because of all of the additional moving components as opposed to the rear.
For example: 4.10's in the rear 4.11's in the front or maybe the other way around.
I can't remember any more. It's too early to really think about it, and I need a coffee.
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Elder User
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From: SW Washington coast
I am trying to go a bit slower ... No need for any speed above 65 ... I remember my old grannied Chebbys would almost go inverted if I could have found some sticky enough tires ...
Right now at idle I have to walk fast to keep up ... I want to be able to walk around it in idle ... I have a c6 right now if that helps ... Not sure yet about the current ratios ...
Right now at idle I have to walk fast to keep up ... I want to be able to walk around it in idle ... I have a c6 right now if that helps ... Not sure yet about the current ratios ...
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From: Virginia
A lot of those trucks like your came with 4.10's. If you happen to have 3.55's, you could get rid of them very easily, since everyone is looking for fuel mileage these days. The sweet setup is the diesel with the 3.55's and the zf 5 speed overdrive.
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The front turns a hair faster for control in mud.
My only data point was a 42 military jeep. Back in the mid seventies when I was a pup the older men told me to not drive the jeep very far at all on the highway because it would wear out the axle gears since they were permanently engages. I asked why didn't they make both axles run at the same rate and was told "the front axle turns a little faster because it improves the steering control in mud. That if they were the same ratio it would still work of course but it would be a little bit more difficult just to keep it running in a straight line; that it would wander a bit."
So I swapped the locking hubs from an international scout with the military jeep. I was just ignorant enough to give it a try. I did not know international used parts from other supplies.
-Jim
So I swapped the locking hubs from an international scout with the military jeep. I was just ignorant enough to give it a try. I did not know international used parts from other supplies.
-Jim
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