JkJeeperDave

I have a 2010 jku stick shift with 315/70/17 tires on it. It also has a detroit locker in the rear. It has stock gears on it now and I was wondering what the best gears to switch to with my set up. I also have been looking into the ripp supercharger. I am thinking I should do gears first and then go from there, but I wss also wondering if i would need to regear it again if I got a supercharger later? Thanks for any help

nthinuf

The folks at Ripp suggest regearing before adding their s/c.

For a 3.8 manual and 35's, 4.88's are popular. Some like 5.13's, and others like 4.56's. Read through a few dozen of the thousand other 'what gears should I get' threads and find replies from people with the same engine/trans/tire size, who live at a similar altitude, who drive in a similar manner - (high speed freeway, all in town, a bunch of crawling offroad, at elevation with lots of hills, at sea level with totally flat roads, etc, etc, etc...)

mhockey9090

Do a quick search and see if you can find any of the previous threads asking about gears. But if you're looking more for highway usage and don't plan on upgrading to 37s, I'd say stick with 4.56s. But if you want a little more, than 4.88s would be good as well. Im running 4.88s on 35s and loving it, compared to the original 3.21s that came in it. Theres a lot of threads around here about running 5.13s in these stock axles, they tend to grenade after awhile (not everyones) , due to how much thinner they are. Plus if you're not upgrading tires then theres no need.

nthinuf

Again, read into the replies you get. 2012 and newer JK's have a 3.6 engine, not the lower powered 3.8 that you have, and generally lower (numeric) gearing wants/needs...

mhockey9090

Seems like a lot of guys are running 5.13s/5.38s and 37s on the 3.8. But if OP is not going to upgrade to 37s then I would still suggest he run 4.88s.

JkJeeperDave

Does the 3.8 have enough power to push 37's after regearing? Is there a better chance of the lower gears grenading with bigger tires?

bluebear

I ran 37s (3.8 liter) with 5:13 gears and it was gutless. I recently went to 35s and it's not so unbearable, though obviously still a dog. You can't polish a turd either way you slice it but it's a Jeep, not a Ferrari.

nthinuf

Too much personal opinion involved, this is where reading through a bunch of replies will help you form your own opinion. But again, it will depend on the ratio, the transmission, the engine, the location, the usage, individual personal preference, and so on.

I have a 4door 3.8 'auto', and ran 5.13's with 35's, then swapped to 5.38's with 35's, and am now on 37's. I live at altitude with lots of hills and elevation changes. It is acceptable, but I would definitely like more power. Manual 3.8's are better off than us auto guys, and usually gear one ratio lower (numerically).

JkJeeperDave

Thanks nuthinuf that helps quite a bit. I appreciate eveyones help and advice

JK505

I'll throw my $0.02 in

I've been running 4.88 with 35's and a 3.8L manual for about 2 weeks now. Coming form 3.21's holy crap it's low. I plan on going to 37's and think it'll be great then but its a lot for 35's. The plus side is I can run 45 mph in 6th gear and still accelerate uphill and get decent fuel mileage but it guzzles gas on the highway (about 11-13 mpg) if that matters to you. Also keep in mind I live under 300 ft above sea level and I'm sure elevation would make a big difference. Either way, I think you'll like it.