What obsession with gas milage? Where? I just want my Jeep to get it out it's own way. The fuel efficiency is just a nice benefit of the engine not having to fight the vehicle as hard as it was before.
Upgrade to 3.73 or 4.10 gears with 31" tires?
- Thread starter Pat Goode
- Start date
Nothing personal, just the whole aim of the question I posed was to do with off road performance.
Many of the reply and threads I could find all concentrate on comfortable highway running and gas consumption. Here in the UK even though fuel is expensive distances are relatively small. It’s also rare to be able to travel any distance at more than 60mph
Many of the reply and threads I could find all concentrate on comfortable highway running and gas consumption. Here in the UK even though fuel is expensive distances are relatively small. It’s also rare to be able to travel any distance at more than 60mph
Here is something interesting. Many of these gearing discussions involve telling people to gear lower than they think they ought to. We do this primarily in an effort to improve on road performance. I'll repeat that. Lower gears. Will this push for lower gears also improve the off road performance?
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'99 SE, 31" tires. My on road performance is at the lower edge of acceptable with the 5 speed. BUT, and this is the money shot for me, my off road performance is unacceptable in a situation that I encounter frequently. Going uphill in "narrow" terrain where the optimal speed is crawling or walking. I have to get into 4lo even when the conditions don't warrant four wheel drive. I just don't have the low speed grunt with my 2.5 to drive in those conditions. Gears are a reasonable response to that issue. 4.10 to 5.13's. Still works on the freeway for any speed I'm likely to want to go.
That's what you get for being a few cans shy of a six-pack.Oh, you folks are talking 4 liter sixes...never mind.
Well the distances I travel, gas is a MAJOR concern, while the pony express trail is only a day long ride, the only gas I found between Tooele and Wendover NV was my gas can... and it is an area that you dont want to run out of gas...and there is no gas at Gold Hill, its a ghost town. That is why I have a 4.0 low range, the higher gears allows for better milage on road and mild manners off road.
Maybe. Maybe not. Yesterday, I pulled 16.3mpg out of my 5 speed/33s/4.88. My 75mph is at 3k rpm.
Higher ratio gears don't always and don't necessarily mean better mpg, that's an old wive's tale. The engine gets its best mpg when it's operating at its most efficient rpm which is not too high and not too low.
After my previous TJ was stolen, I bought a TJ with 4.88 gears, 35" tires, and the 42RLE transmission. The engine rpms were too low on the highway at around 2100-2200 at 70 mph, the engine was always on the verge of lugging. It never reached 12 mpg, it was always in the upper-11 mpg range. Then I regeared to 5.38 this past December which brought my 70 mph rpms up to around 2600-2650. My mpg shot up to 14.38 on its first long trip from San Diego to Barstow and back. It's been in the upper 14 mpg range ever since. Here's where I first announced that mileage improvement after regearing to 5.38... https://wranglertjforum.com/threads...-gears-new-5-38-sweet.7570/page-3#post-114824
And I dare say that offroad behavior is even better with lower gears when in 4Lo or 4Hi. That's because the Jeep can crawl slower with the lower gear ratios like I use. I dunno how a higher ratio that would force the Jeep to crawl faster over tough terrain could possibly make its manners milder. Crawling slower is always the goal of those who do the toughest terrain since it gives them better control at the slower speed plus it gives more torque/power for climbing up & over obstacles. If you are referring to the Jeep being more responsive in 4Lo with lower gears, that's simply inexperience and lack of right-foot finesse. RIght-foot finesse comes with more experience.
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MonkeyMike
TJ Enthusiast
Thanks, Jerry...I think you just answered my question...No, all of my ratio recommendations are always made with highway speeds in mind. Even when I recommend 1 size lower ratio, like 5.13 over 4.88, it's always made with highway rpms in mind as well.
Edit: I just re-read what you said for the third time and think I know what you were getting at. If a Jeep will never be driven on the highway, you can gear to a lower ratio than you'd want if it were also driven on the highway.
Bringing an old thread back to life, are there any downsides to running 4.56 gears with 31s on a 5spd manual 4.0? What would rpms be at highway? I don’t DD it but I drive highways to get to trails. I do realize 4.10 is optimal but trying to futureproof the Jeep if I ever decide to go 32/33s in the future. @Jerry Bransford
RPMs with 33" tires with 4.56 would be just over 2550 at 70 mph. With 31" tires they'd be close to 2750 rpms at 70 with 4.56, not bad at all. Your engine wouldn't complain at all about those rpms. I doubt your mpg would suffer much either.
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Thanks Jerry. Also is it true that running “overgeared” is a benefit off road when crawling?
http://www.grimmjeeper.com/gears.html
Just posting this link again. Appears to be very useful for comparing ratios.
Just posting this link again. Appears to be very useful for comparing ratios.
Using the grimmjeeper calculator, I want to make sure I’m entering correct info. I have 2003 x 4.0 manual. So transmission is NV3550 wide ratio, transfer case is NP200, not sure what my underdrive is. Would this be correct? Anyone know the underdrive?