I recently upgraded to 35s on my '10 JKUR running 4.10s and auto. I was just curious the long term effects of being undergeared on the the transmission and engine and if anyone has had problems? Read a few cases of people having problems and vice versa. I'm content with the current power, just need to pick up a ProCal or Superchips.

 

I've been running 35s and 3.21's for over a year now with no issues. The jeep runs and drives just fine.

 

I have an '09 JKU Rubicon and it's been running 35" Toyo MT's on the stock 4:10's for as long as I've had it. It's been doing just fine. I have no plans to change gears since I am happy with the way it is.

 

Wait until you try a 4:88. I ran a 3:21 for about 6 month. Just got regeared and I must say... Major gain in power back

 

Almost 5-years is as long a test period for JK model you'll find. My 35s went on with auto box and 4.10s and are running strong on my daily driver. No problems.

I ran over two years like this, then has been another two years since reprogramming with a Procal, the Procal is highly recommended, it made it a more comfortable ride by changing the gear change points and lower rpm on highways, improving mpg from 11-12 to 13-13.5

I expected to have to upgrade to beefier axles and regear to lower ratio however it's been reliable and comfortable enough not to spend the $.

 

my only problem is no freeway power. if i have a headwind and the a/c is on i cant even stay in o/d doing 65. its constantly upshifting to find power.

 

As you said, get a tuner. It will help restore some lost power and correct the speedo and shift points. In the mean time, keep the overdrive off on the interstate to help with the gear hunting and power loss you will have

 

exactly, you want to get your shift points on but, with that, i found that running 4.10's and 35's was just fine.

 

Going to shoot for 5.38s since I see myself running 37s in the far future. I was going to regear now just to get it out of the way, but it seems like people have had transmission problems are far and few between. Money is going to go to a spare/ProCal instead.

 

I wouldn't go near 5:38's with an auto... Stick with 4:88 gears anything lower would be overkill