a4x4high

So i know this topic has been beat to death but I really need help deciding . So I have an 07 jku x with manual trans and 35's I need to regear but dont want to over do it . My jk is my daily driver half in town half highway 5 days a week on weekends when i go hunting im on the highway with a speed limit of 75 so i am usually doing 80 or 85 . I am thinking 456 would be better cause the rpms with 488 and 85 mph would be over 3000 rpm for the 2 hrs im traveling. I do pull a trailer now and again with moderate weight on it . So maybe someone could tell me what their true rpm is at 85 with either gear ratio . I dont want to be limited to 70 or 75. Thanks in advance.

medbender

I think its gonna come down to a choice as to what you'd prefer. I myself would gear lower for towing and slow it down on the highway. my 07 auto did well with 5.13 so i think the 4.88 would be good. I've never herd anyone say they wish they'd went with higher gears

TheTerminator

At 85mph your rpm will be:

4.88 gears: 3443

4.55 gears: 3210


If you currently have 3.21 gears, you can drop it into 4th at 85mph and see how you like it. It will put you at 3371 rpm. If you have 3.73 gears, you can try 5th gear at 85mph, that will give you 3133 rpm. That way you can decide for yourself which gears you want.

Incognito

There's actually been a (very) few posts on this forum from folks which regreted their final gearing decision because they where persuaded out of getting 4.56 (mostly by auto shops) and ended up regearing with 4.88. There are however no negative posts (that I could find) from folks who have gone with 4.56.

I have been studying this topic almost non-stop for the last few months as I'll be forking over $1700 bucks next month for a re-gear myself, and to me that's a substantial amount of money. From what the OP has described will be the main use for his Jeep I think he's making a good choice. I myself am opting for that ratio for similar reasons.

The way it boils down is:
4.88 is good off road with decent on-road manners and acceptable highway use.
4.56 is decent off road with good on-road manners and excellent highway use.
YMMV

If you search on here "4.56 gears" you'll find a few reviews, mostly from around 2010.

Here's a few good threads:
https://www.jk-forum.com/forums/modi...t-read-229401/
https://www.jk-forum.com/forums/modi...e-chart-98709/
https://www.jk-forum.com/forums/modi...ar-not-245575/
https://www.jk-forum.com/forums/modi...rs-ftw-186898/

blue project

I'm running a 33.5 mounted tire with 3.73 gears on a 2dr auto. I can run 90 MPH without any issues. Off road lacks a little. I was talked into 4.88. Just sold them. They are way to high for highway driving. I will go 4.56 eventually. I know there more costly by about 100 bucks but people need to know all their options and why!

Stuka

I have 4.56's and love them. Personally I think with a 6sp and 35's 4.88's are on the low side, but work. They are a bit lower than my setup.

I have 33's (33.1" tall), but I live in the mountains and do very little freeway. But even when I do its not horrible (about 2700rpm at 70mph). I think they would work great for 35's. I have wheeled with a guy a few times that has 4.88's and 35's with a 6sp and they work ok, but he runs a bit higher RPM than I do.


But going 85mph, you need a different vehicle man. You must be getting horrible fuel economy going that fast. Mine falls like a rock (even back when I was stock) if I go over 65.

EDIT: BTW, you may find 4.56 gears are a bit hard to find if you have an X or Sahara. I am running Sierra Gears and they have been great thus far. Very quiet and good wear so far. Some 4.56's out there are chinese and are more noisy. So shop around.

T.Man

Found this chart, good info even though it is for the Penstar.

Stuka

Chart for the 3.8L:

a4x4high

I say 85 cause that would be my max speed . The highways around here have speed limits up to 75 so I would be ok at 75-80 being max due to not wanting to be on the highway going less than the speed limit. Im not really concerened about mileage cause like I said most of my driving is back and forth to work with only half my time on the highway which is a 55mph limit so 60 is usually tops for that. I talked with my gear guy yesterday and he tried to talk me into 4.88 till I told him what my jeep is used for .He said 4.56 would be better mayb 4.1 but his concern is 4.1 might not be enough. He has offered to pull front drive shaft and install used 4.1 gears in the rear so I can see how they are with no charge to me. I just think 4.1 will not be enough when I am off road in the higher elevations of Colorado.

Stuka

Being you drive into the mountains (Which are similar to ours out here) I would really suggest 4.56's. I think 4.10's would work for daily driving without any issues and be better for the freeway. I have a good friend with 4.10's and 35's with a 6sp and it works fine. But its a Rubicon, so he has a 4:1 low range. Which makes a huge difference offroad compared to the 2.72:1 low in my X. And he cannot accelerate in the mountains up here as well as me. Yes he can just downshift to a lower gear, but the gears are longer, which makes it harder for the engine to pull through them.