13_gecko_rubi
New member
But what you dont realize is that your 3.6 cannot hold those low RPM at high speed with larger tires. My JK on 37s with 4.88s could never hold 5th at the slightest inkling of a grade it would drop to 4th. At even a mild grade it would drop to 3rd. If I were going to run 37s in my JL I'd do 5.38s in it. 5.13s would be as low as I would go. You need the 3.6 higher in rpm range where it makes torque to spin those heavy meats. Many folks try to run lower gears being their DDs thinking the will get better FE. Well the moment it drops from top gear down its worse than had u run deeper gears and held top gear.Thanks! That's a nice calculator.
With our nice 8-speed tranny the difference between 5.38 and 4.10 gears (all else being the same) boils down to what happens at very low and very high speeds; at moderate speeds the Jeep with 4.10s is just one gear lower than the one with 5.38s and who cares? But at high speeds the engine spinning the 4.10s is running slower, making less noise and probably getting slightly better fuel efficiency. At very low speeds the one with 5.38s is spinning faster making a bit more power. The one with 5.38s will probably win a drag race, but not by much. It will also crawl slower at a given RPM but again, not by much: 5.38s at 1500 in 1st gear low range on 37" tires will be going 1.6 mph, the one with 4.10s will be doing 2.1 mph. Does that matter?
I prefer lower RPMs at high speed. If I cared about acceleration I'd buy a Tesla :yup:
Now the JL wide range trans ratios makes gear swaps not really necessary. You can run 4.10s all day with 37s and it is quite liveable. You just need to understand you now have a 6 or 7 speed, not an 8 speed. It will be hard for most to justify gear swaps. But if u do it do it right and hear for 8th.
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