In this video I’m working on a 2024 Jeep Wrangler JL 4xe (Willys) that a former class alumni brought to me because he wants it set up to run the Rubicon. He’s moving from 33s to 37s, and that’s where a lot of people get it wrong—because tire size changes don’t mean you should blindly jump straight to 5.13s. I break down how ring-and-pinion ratios actually work, why Jeep’s driveline is tuned around the factory setup (this one starts at 4.10s), and my rule of thumb: generally, go one gear “deeper” for every 2–3 tire sizes you increase. I also explain the stuff people forget to factor in—axle size limits, tooth thickness, and why going too deep can literally make the gear teeth too thin on smaller front axles. I’ve lived that mistake: I ran 5.13s in a Dana 30 on my old JK Sport and blew through four sets in six months. When I corrected to 4.56, it drove better and stopped eating gears. On this JL 4xe we installed Yukon 4.88s front and rear, set backlash and pattern, then handled the tech side: the TCM/ABS lit up like a Christmas tree until we reprogrammed with a Tazer Mini JL. Finally, I walk through break-in basics—short drives, heat checks (160–220°F), and why the rear gets monitored first.