Friend told me my gearing was way off after a trip to Big Bear

Last month I took my Jeep up to Big Bear and it struggled on every incline. A buddy who builds rigs for a living rode with me and said my 4.10 gears were wrong for my 35s. He explained I needed at least 4.56 or 4.88 to get the power band back. Swapped them out last weekend and now it crawls like a whole different truck. Anyone else run into this after throwing bigger tires on their rig?

3 comments

3 Comments

keith26411d ago

Told my wife the regear cost about the same as a nice weekend getaway. She didn't buy it either.

xena_kim11d ago

Read a really detailed breakdown on one of the Jeep forums about this exact thing. Apparently the 4.10s are fine if you're staying on stock rubber but once you go past 33s the math just falls apart. The guy explained how the engine has to work way harder to turn those big tires and it basically kills your low end torque for climbing. I remember him saying something about the effective gear ratio being like dropping a whole gear lower than what you actually want for crawling. Makes total sense after seeing how my buddy's JK with 4.88s and 37s just walks up stuff my 4.10s would have cooked the transmission on.

sanchez.mary9d ago

Yeah but here's something I don't see anyone talk about enough - the whole transmission tuning thing. I mean when I went from 4.10s to 4.88s on my old rig it wasn't just about the gear ratio math. The shift points on the automatic were totally different after the regear. It's like the computer was trying to shift at the wrong RPMs before and it made everything feel sluggish even though the numbers said it should be fine. @keith264 probably noticed this too if he actually went through with it instead of that weekend getaway. Maybe it's just me but I think people overlook how much the stock programming fights bigger tires even before you touch the gearing.