Topic: Help me love my TJ!

[stan98tj]

ive always wondered about gearing. im only running 31s but i too have been bitten by the bug and would love some more power. i have a few bolt ons..AEM, 62mmTB and spacer, and a junk "higher flowing exhaust" that im lookin to upgrade to a banks. if i were to regear, what do you guys think i should gear to? i dont really get all the ratios and stuff so im lookin to find out what it would do for me, ie: highway ride, off road, efficiency etc oh and of course, cost. i have an auto by the way.

[FourbangerYJ]

ive always wondered about gearing. im only running 31s but i too have been bitten by the bug and would love some more power. i have a few bolt ons..AEM, 62mmTB and spacer, and a junk "higher flowing exhaust" that im lookin to upgrade to a banks. if i were to regear, what do you guys think i should gear to? i dont really get all the ratios and stuff so im lookin to find out what it would do for me, ie: highway ride, off road, efficiency etc oh and of course, cost. i have an auto by the way.

With an auto I would think the 4.56 would be a good choice. But I am no expert when it comes to the auto stuff. With the sticks the 4.88's would be the ones to get.

[jdarg]

Folks may disagree but 4.88 will work great with 31" tires. Its simply not possible to overgear the 2.5L with the stock axle ratio options unless you are still running the 205's IMHO.

[FourbangerYJ]

Folks may disagree but 4.88 will work great with 31" tires. Its simply not possible to overgear the 2.5L with the stock axle ratio options unless you are still running the 205's IMHO.

The auto tranny does not have a OD. Their 1:1 in D. I do agree with running low gears. The mileage can suffer thou.

[VA_YJ]

I got the Banks header and stinger exhaust, AEM Brute Force CAI, 4.0 TB, ported intake, mustang injectors, brass contact dist. cap, hot coil (everything except the e-fan which I have sitting in box).  The bottom line is that my 4 banger pulls harder than stock (verified by my bud who drives a bone stock '93 YJ), gets a slight increase in mileage, and with a slight increase in top end.  These gains occur primarily at high RPMs, with a slight reduction in low RPM torque and a louder exhaust.  The great thing about regearing (next on my list) is that you get both on-road and off-road performance improvements (with no increase in noise).  Some folks get better mileage with the 4.88 ratio than the 4.10 because they have larger than stock tires and they're out of the powerband.  Running a manual with 31s and 4.88 gears is the equivalent of having a tow package on a pickup.  Better perrformance with minimal impact on mileage.  My advice is to regear first, the add some engine mods over time, starting with the 4.0 TB.  And if you get the itch to run 33s, you're all set as far as the gearing.

[stan98tj]

why would providing more power by re-gearing hurt my mpgs?? does a regear require heavy tires in order not to hurt ur mpgs? are 31s too light? would regearing ever improve the mpgs?

[sharpxmen]

why would providing more power by re-gearing hurt my mpgs?? does a regear require heavy tires in order not to hurt ur mpgs? are 31s too light? would regearing ever improve the mpgs?

i think best mpg you get at stock ratio with stock tires - that's how it was calculated for 5th gear on the hwy and i think it's for 55mph/90kph if i'm not mistaking - so given you drive at that speed for a certain distance and compare the stock with a rig that has 33s the stock wins even though you have less rpms with the 33s. Dunno if that is the same for city driving. now if you have 31s, in that case I think (from what i recall) you're close to stock final ratio is with 4.56 - so that would give you closest to stock mpg - won't be identical, but the closest you could probably get. For city driving you could get better mileage with a lower ratio like 4.88s b/c your engine will need less torque/power to accelerate the vehicle, but that again depends on the style of driving, so the comparison only works if you are driving to achieve the same result (for example starting from a traffic light you will get to 35mph in the same amount of seconds) - but usually when you have a lower ratio you take advantage and accelerate faster and that results in a decrease in mpg (increase in fuel consumption) - and nothing really you can do about that other than putting a brick under the pedal. same with hwy driving, the faster you go the more power you need so the less mpg (and you would be able to go faster in the 5th with lower gears).