4.56 or 4.88?

roaniecowpony

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It is really mass, not gravity that you are fighting on level terrain.
A stationary mass will resist acceleration. A mass in motion will resist deceleration.

To maintain a steady state of motion at highway speed, the largest force a jeep has to overcome is aerodynamic drag.
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roaniecowpony

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The calculators essentially assume operation in a vacuum and zero-gravity.

Bigger tires - and usually a lift - you're sitting higher, catching more wind, you want a little deeper gear to compensate.

Similarly a larger tire is heavier, it takes more to get going and keep going. None of this is accounted for in the basic math of revs per mile, kilometer, whatever
Very true. It's gonna take more horsepower to get the jeep going and keep it going with bigger tires and a lift. Put on 200lbs of skidplates, 300 lbs of those retracting slider steps with their skid plates, another 100 lbs of larger tires, a HiLift at about 40 lbs, 100 lb winch, 250 lbs in steel bumpers and you added nearly half a ton. That's going to make your jeep accelerate like a steamship and brake and handle like one too.
 

D60

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Very true. It's gonna take more horsepower to get the jeep going and keep it going with bigger tires and a lift. Put on 200lbs of skidplates, 300 lbs of those retracting slider steps with their skid plates, another 100 lbs of larger tires, a HiLift at about 40 lbs, 100 lb winch, 250 lbs in steel bumpers and you added nearly half a ton. That's going to make your jeep accelerate like a steamship and brake and handle like one too.
Sure, and the substitute for less-than-ideal horsepower or torque is additional gear reduction. I know someone will want to clarify horsepower vs torque but the fact is it doesn't really matter for the purposes of this discussion.

It's arguably a less-than-ideal substitute but unless one is going to install a blower or do an engine swap, it's the most practical way to go.

Braking and handling...that's another matter.
 

The Viking

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A stationary mass will resist acceleration. A mass in motion will resist deceleration.

To maintain a steady state of motion at highway speed, the largest force a jeep has to overcome is aerodynamic drag.
Ummm, yes. Aerodynamic drag is where most of the energy goes other than heat for an average internal combustion vehicle at highway speeds. What I said is that it is mass, not gravity that the gearing charts usually don't take into consideration. The larger wheels and tires put far more weight farther from the axel and greatly increase rotating mass which destroys acceleration. On a level road, gravity would increase energy loss to friction a bit but not enough to make much of a difference. Rotating inertia makes a huge difference.
 

roaniecowpony

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... Rotating inertia makes a huge difference.
Not to mention the longer moment arm of the taller tire acting on the pavement. Both of which conspire to reduce acceleration. Without a gearing change, my gut tells me the longer moment arm has the bigger effect on acceleration. I had a reason to accelerate and brake aggressively with jacked a vehicle with large tires. There was no discernible difference in my casual observation. The brakes will stop a large tire from highway speed almost instantly when the vehicle is jacked off the ground. On the actual highway, it's a completely different outcome for the taller tire.
 
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I am looking at getting 4.88 gears. Running 37s.
 

Krondor

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I am looking at getting 4.88 gears. Running 37s.
I'm going to get 4.88 eventually as well. Just want the extra grunt, even if I don't jump up to 37's.

Luis,

Sounds like you spend a lot of time in the city, so the 4.88's have my vote for your needs. GL and report back your feelings after moving to the new ratios. :like:
 

Oletimer

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I need some feedback of those who have 4.56 or 4.88, how do you like them? Pros/cons?

I have MT Sport with 35’s and trying to decide what gears to get.

Any advice is much appreciated.
I just went with 4.88 on 2020 jlr with 35s with manual.
I think its perfect. 2600 at 70 . Runs 6th almost always.
 

Dogboyslim

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I just went 5.13 on 34" tires (315/70/17) with the MT. At 70 mph my rpms went from 1900 to 2500. Keeps the speed, mpgs about the same, since before I just left it in 5 at 2600 rpm. It also brought the gears/speed mix back to what I'm used to for a MT. Similar speed/gear ranges as I use in my accord now. So for what its worth, I'd vote 4.88s between the two you mentioned. I think you'll be happy.
 
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WildCatguy

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I just got my Jeep back from the shop. I decided to go with Dana Spicers 4.88’s.

What a difference it makes, the Jeep is now fun to drive with the MT, I got my acceleration back (even more than when it was stock) and I got back 5th and 6th gear on the highway.
 
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