JKRoobi

I've read every thread that I seem to come across on the subject of gears here on JK-Forum. Some people do it for offroad performance (crawling, etc), some for MPG, some do it to keep from downshifting all the time out of OD. Most of which do it for all the above, BUT it seems as though ALOT of people seem to be doing gears for the simple reason of being able to keep there jeep in OD...

Now, correct me if I am wrong, but this is where I get somewhat confused...If your driving in a hilly terrain area or towing, ALL manufacturer's (not just Jeep) recommend to turn your OD OFF while in these conditions (to prevent constant downshifting and/or high transmission temps).

I by all means am for gears and plan to get some for my jeep for various reasons down the road...but I also still plan to turn my OD OFF while towing/driving through hilly terrain. I live in northern ohio where it is primarily flat, but I do drive down to southern ohio quite a bit and notice a difference when I am in the hills...downshifting starts & in turn my fuel mileage goes down the shitter. But, I hit the magic button to turn the OD off and I no longer have a performance issue, nor do I have near as bad of MPG's. Doing this just seems to put the JK back in the sweetspot power range...Just curious why everyone seems to want there JK to stay in OD when they probably shouldn't technically be driving in OD anyways

Again, I'm not knocking anybody by any means, just something I was thinking about and would like some others inputs on this. Thanks~

grim_creation

Its not so much that they don't turn it off in the hilly terrain. Its more of the fact of, people who regear are running bigger tires. They don't have that power you do with overdrive off regardless.
Its also the fact that with bigger tires, they can't stay in overdrive even on flat, level ground.

Sent from my DROIDX using Tapatalk

JKRoobi

I understand that, but for the last 2 weeks, I personally have been running a set of my buddies 35's on my Jeep. I wanted to see personally how bad it was. I returned them to him over the weekend while it was nice out and I didn't think it was all that bad. I did notice the issue while driving in the hills, but as I stated, I turned my OD off and boom...no more problems...

Yamaha90

Mr. Roobi, i would hold off on gears for the time being. Wait until you get your 35's and see how the 4.10's treat you. I have 4.10's in my Jeep and they are pretty good with 35's on the street. OD off i used today as i fought and cussed out the wind on my way home and it was fine. Maybe my superchip made a difference too, but my Jeep is definately drivable. The only reason i would get gears is to get back that acceleration i lost when i upgraded tires, and i'd only upgrade if i got a deal on the gears.

JKRoobi

Yea, that's exactly what I plan on doing...especially after feeling first hand how it was going to be. If needed later, I'll do gears, but thats a good way's down the road...

nthinuf

There is no magic to it. Turning OD Off simply forces the transmission to use 3rd instead of 4th. Like a manual guy not using his 6th gear. Why don't more people turn it off? No clue. It has been talked about on this site for years, and is a viable way to run bigger tires until you get around to regearing. The downside is that you lose your low end. (sucks when you have traction, but simply don't have the oomph to make it up a hill and have to drop into 4-Lo to keep moving)

If you want to look at the numbers, plug your tires size and gear ratio into the chart in the faq's to get your OD On rpm @ 70. Then divide that number by .69 to get your OD Off.

With your stock 4.10s and 35's, having OD Off put you right in the sweet spot rpm range for this engine. Again, no magic to it.

MOPWR2U

I don't know about you guys, but lower gears have kept my Jeep from downshifting to second gear all the time. Turning OD off to cruise down the interstate at 75 mph isn't that bad, you can do it all day long. With a 4.10 geared Rubicon and 37" tires you're going to be turning 3000 RPM in third gear. I would suspect a 3.73 geared Jeep with 35" tires would be turning about the same RPM. But when you get into the hills, and your Jeep has to downshift into second gear, and suddenly you're engine is turning 4700 RPM for miles and miles and miles, well, that really sucks. My worst trip was a 50 mile trip where the altitude increased by 3500 feet, and I was driving into a headwind. My Jeep was in second gear for almost the entire 50 miles, and I used 10 gallons of gas to drive 50 miles. Yeah, 5 mpg gets old in a hurry. I've done the same trip numerous times since, and with 5.38 gears my Jeep can at least stay in third gear, even with a modest headwind.

jimk403

I would think it also depends on the terrain where you live. Half my family lives in Ohio, so I'm familiar with it. If I lived there, gears might not be such a big deal. The hills here in SoCal taxed the JK stock, regearing allowed the engine to run in an rpm range where it makes more power.

Red Dog

Doing your gears returns the rpm’s to their original range after you put on bigger tires. Bigger tire without gearing can cause premature ware to the clutch if you have a stick. I found that out one day fallowing a guy with big tires and he didn’t do the gears. So he spent the day slipping the crap out of his clutch as he went through the rocks. it stunk!

Mark Doiron

I know I've read that, too, but that's not really a good reason to regear unless it's a purely trail rig. That is, when you regear you're going to have a much greater impact on your highway performance--it's not like you can get away from that. Regear for that. If crawling performance doesn't suit you, maybe you need a different transfer case.