I ran 33s on 4.10s for 2 years on a 2010 auto. It did ok but with any head wind or incline on the hwy you are going to be downshifting. If you are going to regear don't go to 4.10s, it 's a waste of money even if labour is free. Do yourself a favour and run a lower gear.

 

I'm afraid of loosing my milage by gearing down. I know I will be downshifting. But to a less extent with 4.10s and the power adders

 

Power adders only make a material difference at higher rpms. Look at the charts above. What is the HP at 2000 rpm stock, with a tune, and with a premium tune, all compared to running at 2500 rpm.

Downshifting hurts fuel economy more than running at 2500 rpm--the exact opposite of what you are thinking.

When the transmission downshifts--referred to as flashing the converter--it shifts into 3rd gear with additional slippage to increase rpm levels in order to produce more power.

You can test it out to experience what I am saying.

Drive a hill you know will result in a downshift. Notice the rpm levels in 3rd gear surge and then back off.

Then, drive the same hill at the same speed in 3rd gear, with the OD turned off. The converter will be locked. As a result, the rpm levels in 3rd gear will be less than they were when the transmission downshifted.

If you want good fuel economy in an automatic, gear low enough so that your vehicle does not frequently downshift.

If you want good fuel economy in an 07-11 and will run 33" or taller tires, run as low a gear possible--5.13s for a non-Rubi and 5.38s for a Rubi.

Regardless of gearing, economy will drop off over about 70-75 mph. With a non-aerodynamic vehicle like a jeep, you aren't going to get 20 mpg at 80 mph.

 

Nope. I travel at 60-65mph. Or 100-110 kph. There is not a lot of time I downshift actually. Crisis most times at 1900rpm highway. I run 265s in winter and running lightweight 285s in summer.

 

All the reason more to regear as low as possible--you won't run high rpms even with the lowest possible gears. With 5.13s or 5.38s, you will get over 20 mpg at 60 mph and almost never have to worry about downshifting.

 

planman, the op is dead set on 4.10 gears and just posted this up to find one person to tell him what he is thinking is right. Let him learn from his own mistakes.

 

Lol. Good point.

 

I agree with most of the posters. If your going to spend that kind of money to regear I would definitely want to notice it. You want need a cold air intake or power adders if you gear to 4.88 or 5.13. It will be a whole new animal (the jeep). A couple of mpg, if that, will be worth the torque. I actually think if you drive 60-65, like you say, your mileage want get worse. These things were geared wrong from the factory.

 

Gotta give it to him though, planman went all out.

Charts, numbers, data, facts. Two thumbs up to you sir

 

No. I'm trying to understand gear and how it relates to my jeep and how it affects milage. I have always been under the understanding that gas milage is better if you run lower rpm most of the time. I really don't think I need 5.10s etc. I'm never going to run huge tires and I do run 265 in winter.