[Keith]

I have a 05 Unlimited JK with an auto trans and 3:73 gears with 30 inch tires. I would like to jump to 32 or 33 inch tires but have heard that it will dog in O/D on the freeway.

 

[Yota Bill]

bigger tires is the same as a higher gear ratio...you heard correctly, but how much of a dog it will be, I cant answer....
there are many calculators on the net that allow you to input the original tire size and the desired tire size and see how that affects engine RPM at a given speedwith your gear ratio, that will help you decide.