4.11 or 4.56

E2 · **Posted:** Mon Mar 22, 2010 1:46 am

w/ 32s?

Why one or the other.....

Jeepin_it_real · **Posted:** Mon Mar 22, 2010 1:51 am

i'd say if you got a pretty heavy wheel set up a 4.56... the goal is to try and restore some power and if you got a heavy set up the 4.11s might not cut it

clacker · **Posted:** Mon Mar 22, 2010 9:41 am

4.56 definatly. Higher is usually better. 4.56 will b better on gas than 4.11 with that tire size. And itll put less stress on ur trans

E2 · **Posted:** Mon Mar 22, 2010 11:49 am

Clacker not sure how you figure more power with the 4.56 gears equals better mpg? I looked at a chart showing that with smaller gears you get better mpg. Am a missing something?

The chart's figures I have were for a manual rpms so I recalculated and figure out a percentage of power. So here is what I have for the 3.73:
Stock:
29.3" tires with 3.73 gears = 100% stock torque power
New Tires: (265/75r16 are 31.7")
31.7" tires with 3.73 gears = 92.43% torque power (A loss of 7.57% power)
31.7" tires with 4.11 gears = 101.85 torque power (A gain of 1.85% over stock)
31.7" tires with 4.56 gears = 113% torque power ( A gain of 13% over stock)

To double check my figures Clacker is this true for you:
33.4" tires with 4.56 gears = 107.25% torque power over stock. (So a gain of 7.25% over stock) Does that feel about right??

Now to figure mpg this I am not sure how to do.......yet. I currently get stock 16.9 mpg as my average all around.

DirtyKK · **Posted:** Mon Mar 22, 2010 12:31 pm

i think you answered your own question with all that math. i would look toward the future though. are you ever gonna go bigger? parts and labor for a gear change is expensive, do you think you will be satisfied with 4.10 in the long run?

tjkj2002 · **Posted:** Mon Mar 22, 2010 8:21 pm

E2 wrote:

Clacker not sure how you figure more power with the 4.56 gears equals better mpg? I looked at a chart showing that with smaller gears you get better mpg. Am a missing something?

The chart's figures I have were for a manual rpms so I recalculated and figure out a percentage of power. So here is what I have for the 3.73:
Stock:
29.3" tires with 3.73 gears = 100% stock torque power
New Tires: (265/75r16 are 31.7")
31.7" tires with 3.73 gears = 92.43% torque power (A loss of 7.57% power)
31.7" tires with 4.11 gears = 101.85 torque power (A gain of 1.85% over stock)
31.7" tires with 4.56 gears = 113% torque power ( A gain of 13% over stock)

To double check my figures Clacker is this true for you:
33.4" tires with 4.56 gears = 107.25% torque power over stock. (So a gain of 7.25% over stock) Does that feel about right??

Now to figure mpg this I am not sure how to do.......yet. I currently get stock 16.9 mpg as my average all around.

You got to figure in the weight of the bigger tires,it's something like for every 1lbs of added rotating weight it's like adding 10lbs to the vehicle.You also got to figure the added weight of all the extra armor and such also.Going to "stock" by the #'s you will still be undergeared and underpowered which equals less mpg's.Going about 10% over will actually get you better power and mpg's.

When I was figuring my gear ratio's for the SFA by the #'s 4.88's would put me back to "stock" with 35" tires,wanting a little better power for city driving I opted for 5.13's.After driving with the 5.13's I should have went with 5.38's with 116lbs each wheel/tire combo here in CO.

E2 · **Posted:** Tue Mar 23, 2010 1:15 am

tjkj2002 wrote:

You got to figure in the weight of the bigger tires,it's something like for every 1lbs of added rotating weight it's like adding 10lbs to the vehicle.You also got to figure the added weight of all the extra armor and such also.Going to "stock" by the #'s you will still be undergeared and underpowered which equals less mpg's.Going about 10% over will actually get you better power and mpg's.

When I was figuring my gear ratio's for the SFA by the #'s 4.88's would put me back to "stock" with 35" tires,wanting a little better power for city driving I opted for 5.13's.After driving with the 5.13's I should have went with 5.38's with 116lbs each wheel/tire combo here in CO.

TJKJ2002 your right. I was thinking about this on my way home. The stock tires are about 40# each and the new tires are 54#. If your right about the rotating weight 14# each tire will make a big difference. I figure 4.11 would not be bad with the 32s but once I tow i'll feel the extra weight of rotating those tires and be slower.

I still don't understand how with more power larger gears ie: 4.56 you will get better mpg. As a daily driver I am looking for mpg with at least same stock power or slightly more. The mpg if I loose 1 mpg is nothing 2 mpg is 34 miles per tank and that is give up some.

RRiveraKK · **Posted:** Tue Mar 23, 2010 2:50 am

tjkj2002 is right, it will provide better MPG because your engine is not having to compensate w power (torque) to move a now heavier vehicle. The gear ratio will provide the muscle so your engine doesn't. Hence the reason Jeep put those darn 225/75/16 keeps the KK from becoming extreme gas hogs (This is my opinion). I might be wrong, so take this as my opinion. I can't provide facts for this.

E2 · **Posted:** Tue Mar 23, 2010 5:04 pm

Here is my thoughts on why bigger gears 4.56 versus 4.11 or 3.73 would be better in mpg.

If you have 32" tires and the 3.73 you will be pushing the gas more to go faster but not much response so the more you press the pedal more, but all you are really doing is wasting gas and not moving much faster.

Fulltimer · **Posted:** Tue Mar 23, 2010 5:12 pm

My tires are a full 32.0" and I have 4:10 gears. It is much better than it was with the stock gears. BUT, it is not back where it should be. So 4:56 would be better.

Terry

E2 · **Posted:** Wed Mar 24, 2010 1:59 am

Fulltimer wrote:

My tires are a full 32.0" and I have 4:10 gears. It is much better than it was with the stock gears. BUT, it is not back where it should be. So 4:56 would be better.

Terry

Just what I wanted to hear. Someone's experience! How is your mpg?

E2 · **Posted:** Fri Mar 26, 2010 3:28 pm

clacker wrote:

4.56 definatly. Higher is usually better. 4.56 will b better on gas than 4.11 with that tire size. And itll put less stress on ur trans

Well not sure about less stress on tranny, but more on the engine at higher speeds. Been talking to lots of gear places and they are not recommending the 4.56 as on highway without the need for 4.56 the engine will be at higher rpms and just more of a wear on the engine. So going 80 mph would be a think of the past.

E2 · **Posted:** Fri Mar 26, 2010 3:30 pm

Fulltimer wrote:

My tires are a full 32.0" and I have 4:10 gears. It is much better than it was with the stock gears. BUT, it is not back where it should be. So 4:56 would be better.

Terry

What RMPs are you at when driving on "level" higways or streets at 35, 40, 55, 65, 70, 75?

Currently with stock I am at
70 @ 2100 rpms
75 @ 2200 rmps
Will get the rest of the numbers this afternoon.

Boiler · **Posted:** Fri Mar 26, 2010 4:32 pm

I've heard a lot of people say they get better milage at higher speeds, like 65-70, than they do at 55. My understanding is that they are closer to the most efficient RPM of the engine at the higher speed.

If I understand correctly, going to 4:10 gears would make you drive higher RPMs for the same speed, so you could hit your efficient RPM range without having to go 70+ mph.

I drive about 55-60 and get terrible gas milage. I may have to consider this change too, if my assumptions are correct.

Fulltimer · **Posted:** Fri Mar 26, 2010 5:13 pm

E2 wrote:

Fulltimer wrote:

My tires are a full 32.0" and I have 4:10 gears. It is much better than it was with the stock gears. BUT, it is not back where it should be. So 4:56 would be better.

Terry

What RMPs are you at when driving on "level" higways or streets at 35, 40, 55, 65, 70, 75?

Currently with stock I am at
70 @ 2100 rpms
75 @ 2200 rmps
Will get the rest of the numbers this afternoon.

I'll get you the numbers. I rarely drive 65 and never above that. But in the interest of science I'll do it! :lol:

The RPM's will be higher than stock. My speedo is off so I'll use the GPS for speed readings.

Terry

Fulltimer · **Posted:** Fri Mar 26, 2010 6:17 pm

Okay, here are the results:

35 @ 1,500 RPM
40 @ 1,300
45 @ 1,400
55 @ 1,700
65 @ 2,100
70 @ 2,300
75 @ 2,300

I checked the 70 & 75 again just to be sure. They were the same! That is weird! I had just checked my KJ's weight and it was 4,960 pounds. That would make a difference also.

Terry

tjkj2002 · **Posted:** Fri Mar 26, 2010 9:28 pm

E2 wrote:

clacker wrote:

4.56 definatly. Higher is usually better. 4.56 will b better on gas than 4.11 with that tire size. And itll put less stress on ur trans

Well not sure about less stress on tranny, but more on the engine at higher speeds. Been talking to lots of gear places and they are not recommending the 4.56 as on highway without the need for 4.56 the engine will be at higher rpms and just more of a wear on the engine. So going 80 mph would be a think of the past.

Your engine can turn 5500rpms all day long and no harm will be done.

Your 3.7 does make it's peak HP till about 5200rpm's and the peak torque does not occur till about 4200rpms.The closer to peak torque the more efficient your engine will run(most power also).

When I had my 32" tires on with 3.73 gears I was turning about 2800rpms at 75mph,with 4.10's and 32" tires at 75mph I was turning about 2900rpms.Figure that one out :idea:

With 35" tires and 5.13's at 75mph I'm turning about 3200rpms,gobs of power but 75mph with 35" tires at 28psi is not a fun ride.

E2 · **Posted:** Sat Mar 27, 2010 11:18 am

tjk2002 seems odd the 100 difference between the two gears. but was the power restored from 3.73 to 4.56 ? that is what i am interested in? do you think width of tire will make a difference? ie: 265/75r16 (10.5" wide) or 235/85r16 (9.5" wide) ?

tjkj2002 · **Posted:** Sat Mar 27, 2010 7:18 pm

E2 wrote:

tjk2002 seems odd the 100 difference between the two gears. but was the power restored from 3.73 to 4.56 ? that is what i am interested in? do you think width of tire will make a difference? ie: 265/75r16 (10.5" wide) or 235/85r16 (9.5" wide) ?

The 1" width difference is not a huge deal,not alot more friction from the 10.5 compared to the 9.5.The big difference is the weight,though most 265/75's are "D" rated and 235/85's are mostly "E" rated with the "D" range being a little lighter possibly depending on the tire.

E2 · **Posted:** Sat Mar 27, 2010 7:28 pm

tjkj2002 wrote:

E2 wrote:

tjk2002 seems odd the 100 difference between the two gears. but was the power restored from 3.73 to 4.56 ? that is what i am interested in? do you think width of tire will make a difference? ie: 265/75r16 (10.5" wide) or 235/85r16 (9.5" wide) ?

The 1" width difference is not a huge deal,not alot more friction from the 10.5 compared to the 9.5.The big difference is the weight,though most 265/75's are "D" rated and 235/85's are mostly "E" rated with the "D" range being a little lighter possibly depending on the tire.

I am looking at the BFG ATs the 235/85r16 are 49# and the 265/75r16 are 54#.
So mostly from what I have heard I will go with the 4.11 for my case as I tow a few times during summer and don't carry much weight or passenger when offroading. And the 235 are lighter and less friction. They will be okay for offroading right?

4.11 or 4.56

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