I recently bought some 4.88 gears and had them installed at a major Jeep 4x4 shop in my area. My question is what should I expect out of my new gears. I have to say I do not really notice a huge difference from the 3.73's. I do notice a difference when I am on the highway and I am in cruise control. I noticed that the engine is not shifting to lower gears to stay at the same speed. But I have to say, I dont see all this "More Power" that everyone is getting with their gears. I have an automatic with Cooper 35's. I only have 500 miles on the gears and I have to go back to the shop next week because it is after my break in period. Should I be worried that my gears are not really in my Jeep? And if they are, how can I tell?

 

This "more power" is about low end power... in theory, lower gears (higher numerically) should limit your top-end speed.

Do you notice different RPMs for the same speed? Have you updated your computer to recognize the new tires and gears?

 

I do notice different rpms for the same speed, but I have not updated my computer yet.

 

Get an AEV ProCal or a Superchips...

From your OP, it sounded like you have an automatic... you will want to make your Jeep aware of what gears you have and what size tires you have so your Speedometer will be correct and so your shift points are correct.

 

Thank you for your help. Can the dealership correct my speedometer? What do those ProCals or Superchips run? Are they worth it. Cant I find someone that has one of them re-calcualate my speedometer for me?

 

Basically what you did was bring your jk back to what it'd drive stock with the stock 31-32's while your running on 35's now. IMO, 35's, auto, = 5.13's kinda late for that but a programmer will help alittle.

 

I went from 4:10's to 5:38's, I have a JKU Rubi, auto with KM2 35's and 150 miles on my new gears.

I added (at the same time) CAI and flashed with 87 \tow tune and adjusted for new gearing. I read a lot of positive comments about 5:13's, personally I don't think my 5:38's are low enough for the little amount of freeway driving I do... I feel like it struggles to maintain 70-75mph and keeps kicking down to try and maintain those speeds


Maybe it's time for a S\C or a V8 conversion

 

I paid $150 (I think) for my ProCal.

The dealer will not do this for you. As far as borrowing a friends, these devices lock themselves to a VIN. Once locked they will not work on another vehicle until the first is restored to factory settings.

 

Hey thanks man, 150 is not bad I guess. Are they hard to use? Did you notice a difference?

 

They are easy as cake to use.

As for noticing a difference... I have a standard transmission, so ALL this did was allow my speedometer to be correct so I wouldn't get any speeding tickets.

With an auto you should expect a little something from getting your shift points back... but what you might find more interesting is the Superchips, it a whole engine tuner in addition to what the ProCal does.

http://northridge4x4.com/proddetail.php?prod=SCHIP-3875