Given my choice, I would have done 4.88s when I geared mine, but covid supply was a thing and 5.13s popped up available before 4.88s did.. It would have gained me a few more mph before the second stage of the oil pump kicked in, but most of my driving is at 75 or so and I like pulling hills with the cruise on and not downshifting, so not a huge change for me..
You do realize that any jeep built before 2003 needed the gearing because the transmission had none? The 32rh in the tj had a 2.7-1 1st gear. The zf in the gladiator has a 4.7-1 1st gear. A tj would need 7.13 axle gears to match a gladiator with 4.10s. You have all the rpms you want from a simple press of the throttle automatically. Even with 4.10s if I'm trying to pull a step grade at 85mph, the trans downshifts and the pentastar puts out it's peak horsepower at 6000+ rpms. The transmission has all the gearing you could ever need baked right in. It makes power at high rpms, that doesn't mean you should be cruising around down hill with a tailwind at 3k rpms. That literally defeats the purpose of having an 8 speed with 2 overdrives. You should only be in overdrive under low loads by design. Anything more and it downshifts. It's not supposed to hold 8th gear under acceleration or up hills, that is why JLs come with 3.45s and 32's. There's no point of having 8 gears of you'll be in 8th at any speed over 40mph.
@Zachanadandy - To be clear though, with having an Automatic the only real consideration here for me is picking the right gear ratio for tires/weight. From there the Jeep does the rest.
I'll lay a thousand bucks that says with 5.13's and 37's you'll never, ever, one time wish you went with 4.88's.
I'll take your money. Went to 5.38s and 38s and hated it. The jeep was better on the freeway with 4.10s. For me there absolutely is a point of too much gear. No better off road as the 4-1 transfer case is plenty low. Worse mpg on roadtrips. In 8th gear at any speed over 40mph. For 37s I'd never go past 4.88s again period. Granted I drive fast but too much heat is too much gear.
We all see you advocating for 3,000 rpm in 5th on an 8 speed because who wants to use the full range of gears.
TBH I bet you feel like your beating a dead horse just reiterating the same answer over and over again. I feel for ya. But if its any consolation, you saved me an exspensive gear change which would have also stopped me from downsizing a tire size which i prefer when DD. My solution is when i need more oomph and i got the cash. hemi swap and keep the stock 4.10s. The hemi's powerband should be able to leverage shorter gearing much better anyway on top of being lighter than a half ton pickup. It would have been just more money pissed down the drain in my case if I had regeared too. I've paid a bit of attention to the hemi swap guys and I've noticed they kept 5.13s or similar when they went to the hemi and then complained why the mpg got way worse. hemi at 3k vs pentastar at 3k sucks way more gas lol. but being in the 1900 to 2300 rpm range on a hemi for highway speeds should really maximize the most economy out of it.
i have 37s and 4.10s. I usually cruise in 7-8th on the highway all the time. I think the main thing that may keep 4.10s from touching overdrive is if you have a really heavy 37in plus setup. I run stock wheels so I'm at or under a 100lbs a corner. But if someone was running some KMC Grenadier Beadlocks they would be at or well over 130lbs a corner. That might need some more gearing because you have rotational mass and tire height fighting you vs just tire height.
where do you live?! Killimanjaro?!
Go with whatever is more readily available and cheaper. with an 8 speed auto your splitting hairs between gears like 4.88 or 5.13. If you have never regeared a vehicle before, your not really gonna know your preference. I will say this. The taller the gear set you go the more small tire sizes you will exclude yourself from. If you ever decide you wanna downsize from 37s for any reason (like international travel, 37s are illegal in most other countries, 34" is the international max 9/10 times) 5.13s on a 315/70 tire is gonna be strung out to say the least. If your exhaust is stock you may never notice but if you have a custom setup like me, tall gear set can mean drone city at highway speeds. But anyway for your case, either is fine, flip a coin.
