bob-o

But with the new pentastar it doesn't really lose much power when switching to 35's or 37's. When I get on the throttle pretty good at a stop light, I actually break traction a little bit on 37's and auto trans

bo9roadking

Yes, get the ProCal. I have used it on my 2012 JKU Rubicon with 35" tires and it works like a charm. I will use it again to readjust tire size when I put on 37" tires.

When the computer has the correct tire size information, it will adjust the speedometer and indirectly adjust the transmission shift points because the speedometer will be accurate again. If the speedometer is off because the tire size is wrong, the transmission will shift at the wrong time. You could also have problems with the computer nanny engaging and causing some weird driving experiences because the axles will be spinning at a different rate than what the computer expects if the tire size isn't adusted.

Arisdocjk

2013 jku sport, 35's with 4"lift. Pro-cal made big difference. No need to re-gear.

mattgt5

I agree, posted that previously. I would never drop $2k to regear a 3.6 with 4.10. The only way to adjust your shift points is to buy a programmer or just use your tap shifter to make it shift

notsoricer

Ok so given there's no wheel slip, are the rpm's and speed of the vehicle not directly parallel in given gears? Lol

scooby snacks

I have a 2012 JKU Rubicon with A/T and 35's. Used the ProCal... no need to re-gear IMHO.

rb1boxer_3

You still lose power though even though it doesn't feel lk it I have 37s on my auto and will be going to 4.88 to get that crawling back up to stock.