I eventually plan to lift my Jeep by 2.5 inches. But I came across a really sweet deal on some 35's. I was thinking about sporting the 35's now, and getting the lift in a couple months. My gearing is set at 3.73

Will this cause any problems both on and off road? My current off-roading only consists of moderate trails and no serious rock crawling. Will I experience significant power/driving performance loss?

 

You might squeeze some 35's in there, it will be extremely tight though. 3.73 will be fine. I would wait till you lift her before you run the 35's. And as far as power loss there will be a bit cause your carrying a heavier tire.

 

Your going to have to cut your fenders to run 35's with no lift. The ride quality and off road performance will suffer. Those tires will not allow the suspension to cycle as would with a lift and more room for travel. It can be done though!