Does anyone know the biggest tire the 3.73 can handle this is for off-roading purposes?

 

3.73's sucked with stock tires...

But the answer will depend on your specific setup (auto or manual, 3.6 or 3.8, rubi or non-rubi tcase, 2 or 4 door, whatever else), the terrain, and a lot of personal preference. If you don't want to regear, and you don't have a rubicon, then start looking for a case to swap.

 

It's not a matter of how big of a tire the gears can handle, it's the loss of power due to a taller tire. The simple answer to your question is 33"-35", any taller and your going to have a serious lack of power. It will also depend on what engine and transmission you have. Read through the gear section on the link below.

https://www.jk-forum.com/forums/modi...bie-has-18617/

 

I have a 2014 rubicon with 4.10 gearing and automatic I think 35's would be max. I am currently running 34's (285/75-17) and they feel pretty good but not sure I would be happy with much bigger. I know people say they are happy running bigger tires but I guess everybody has a different idea about good performance.

 

I've got 35's on my '07 jkr, and the power loss was terrible. Threw in a super chips traildash, and that helped a ton. I would recommend anything bigger than 35's without regearing.

 

I have 33's on a 2012 2dr with 6 speed and hapve plenty of power. Ive wondered though if 3.73s would be ideal to get a little more take off without sacrificing low rpm highway cruising speed. 4.11s would zap my highway mileage I think.

 

I'm running 305/70 X 17's on 373 gears with Diablo tuner and it is just fine. IMO 35's would be the tallest tires on 410's.