Best for pulling a grade or passing? Probably 5th. Best for steady state freeway mileage, 6th. But if your gearing won't allow the engine to get to an efficient RPM, approximately 2100 RPM, your lugging. That means poor mileage and poor performance. And if you are cruising the highways in 4th or 5th, to get reasonable performance, you can't take advantage of the six speed box. You'll know you are in the wrong gear if you step on the throttle and almost nothing happens
4.10 works well with 33" tires, but 35s will probably need at least that and maybe 4.56 to have reasonable throttle response in 6th on the highway.
where do you live? Mountains? flat lands? altitude?
what are the speed limits on the highways you drive on?
do you obey posted speed limits?
Do you wheel mud, rocks, overland? and how important is crawl ratio to you?
where do you live? Mountains? flat lands? altitude? what are the speed limits on the highways you drive on? do you obey posted speed limits? Do you wheel mud, rocks, overland? and how important is crawl ratio to you?
I had 4.56's on my XJ 5spd (same final drive as JK) with 33's and it was totally livable on the highway, even in the mountains. I ended up going to a 4:1 case for rock crawling.
I now have 5.13's in my JKR 6spd with 35's, which measure 34". Low range 1st gear is awesome for rock crawling. It does have the 4:1 case, so, that helps. But, to be honest it is a little busy on the highway. 70mph is getting real handy to 2900rpm, 72mph is 3000rpm. I drive 125 miles a day at 3000rpm (in a 75mph posted zone). Lots of power to pass, no trouble in the hills... 16.8-17.2 mpg (fully armored, and pretty stout armor, so, heavy), one of the slowest vehicles on the road.
If highway was more important to me than rock crawling, I'd have a hard time deciding between 4.56's and 4.88's. Guess it would depend on my need to drive 75-80mph.
I have a 2dr with the same engine as you. I run 35's.
I have 4.56 gears. They were fine for the low elevation flatlands of the Midwest. Now that I live up at a mile high and I get into the mountains, I wish I had 4.88's or even 5.13's. It's not that the 4.56's are terrible. Just that they're marginal for the steep grades and elevation that I wasn't dealing with in the middle of fly-over country.
On the freeway, I get 17.x MPG or so on average.
When rock crawling, I really wish I had a lot more low range. But I have a sport model with the 2.72:1 low range. A Rubicon with it's 4:1 low range would be a better ratio for me. I have the manual transmission and I find that when I'm on an obstacle, it doesn't crawl as well as I'd like. If I give it enough gas to not stall I end up flying over the obstacle too fast. If I don't give it it enough gas I stall. That wouldn't be a problem with the automatic however. And at some point in the future I want to install a 4 speed Atlas transfer case to give me all the low range I'll ever need.
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