With the 4.0? 33's yes, 31's I would run 4.56. Both combos will put you around 2900 at 70.
Post re-gear miles per gallon
- Thread starter Rocky Wrangler
- Start date
That depends on the engine and tire size. The bigger the tire, the more rpms it takes to turn it. You need more power (rpms) to turn a 35" tire than it does a 30". That's why regearing to produce the same rpms with a bigger tire that worked well with a smaller tire doesn't work as well as some people think it will. And a 2.4/2.5L engine requires more engine rpms for a given tire size than the 4.0L requires.
Yeah, it was just an experiment. I usually stayed in the 2700 range, but I occasionally left it in 5th (on the 6-speed) just to see what would happen with the mpg. Here's a rough estimate of my setup during this time.
1st Year
3.73, 6-speed and 31's for 9 months @2700-3300 rpm
3.73, 6-speed and 33's for 3 months @2700-3300 rpm
2nd Year
3.73, 6-speed and 33's for 6 months @2000-2500 rpm
And the down side to getting 4.56 but keeping 31s.. is high rpms on freeway.. which leads to poor mpg and top speed?
Also.. how does this differ for a 6 spd vs 5 spd? Does one setup deal with 31s on 4.88 better thsn the other?
Ok, so for totally self serving reasons (this is my LJ I am describing) 4.0, 285 75R16 (32.8" +-) (may go up in size but not any time soon), 6 speed manual, was thinking 4.56.... what say you?
4.56 would work fine for a 33" tire but with your 6-speed which has lower ratios, many believe it can go one ratio higher like 4.10. I'd definitely say 4.56 for the 5-speed but the 6-speed opens up the 4.10 as a second viable choice. Personally I'd go 4.56 but some are more sensitive to engine rpms so maybe 4.10 for them.
It is a Rubicon so it already has 4.10 gears..... I was thinking 4.56 because of my trailer, on our trip out west it was working pretty hard on some of the highways through the mountains and necessitated dropping down to lower gears, sometimes all the way to third and once to second!
From 3.55 to 4.56 (both on 33" duratracs), I was around 15.5-16.5 average. Didnt change for me. Once the 35s went on and still running 4.56 I am now averaging 14.5
No downside. Like I said earlier, no real difference between the two manuals as far as gearing. The nsg370 will have a lower 1st gear on and off road, the nv3550/ax15 will run a bit less rpm in top gear.
For comparison, the Rubicon came stock with 4.10 and a 29.5" tire.
I've got 4.56 gear ready to go on with the 4.0, 33's, 6-speed combo. I think with this ratio you can run 33's or 35's happily. It's a little overgeared for 33's and a little under geared for 35's. It's a hard transmission to decide gear ratio IMHO. If you're ever possibly going to 35's go with 4.56 for sure.
Since the jeep is an LJ it does have the Dana 30/Dana 44 axle setup and the 42RLE transmission. I turned on the GPS and I am running 70mph at 27-2800 rpm.
I never wanted to break any land speed records with the jeep but I do want to run stuff over and climb things, ya know......Jeep stuff.
I never wanted to break any land speed records with the jeep but I do want to run stuff over and climb things, ya know......Jeep stuff.
That's where I was ...then I regeared to 4:56 and went from 13 to 19 mpg , I was shocked .
What you'll notice is you ''' be going 60-65 and barely be pressing the gas pedal.
I'm in Gatlinburg now and at 40 in 4tg I hit the gas on hills and it accelerates.
I love it .
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