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Hey I have a manual trans with 3.07 gears and 31" tires, it wheels ok but i would like to crawl a bit lower. I also have a 27sp 8.25 axle. Would I notice a gain by swaping in a 29sp 8.25 with 3.55 gears?
It would deffinately be and improvement both strength wise and performance wise. I regeared to 4.56's w/ a 5spd and 32's and the power is nice but if you could get a 29spline 8.25 w/ 3.55's at a reasonable price i would deffinately say go for it. This is exactly what i told my friend w/ your same set up to do.
For 31's I would recommend 4:11 but if you plan to use bigger tires in the future I would wait and get 4:56's then. I wheeled with 31's and 3:07's for a couple of years and it wasn't too bad.
I run 31's and 3.55 gears in my 91 5 spd. It's pretty peppy and first gear in 4low is pretty damn low. It's much better than in my old auto XJ with the same gearing and tires.
X2 those who recommend 4.10 gears. You're never going to go smaller, and 3.55s are such a half-measure. If you're using some sort of calculation to guess what ratio, consider that 3.55 or 3.73 are/should be good ratios for stock size tires, ergo 4.10 with 31s.
i did the swap you are talking about and it was worth it in comparison to what it would have cost to re-gear to 4.10, and yes you can use overdrive on the highway & actually have some passing power. It was the second best thing I have done other than lifting the jeep, plus you get a stronger rear axle.
i went to 31's and regeared to 4.56's. (ax15)
around town it's awesome, on the highway it's 100% acceptable up to 70-75mph... and in the rocks it's perect.
My rig is my daily driver, and once a month spends a day doing a 400mile round trip interstate run.
I have yet to 'math out' the milage, but, I am getting 40-50 extra km's per tank of gas (combined driving) compared to 30" tires and 3.07's.
31's and went to 4.56's in my MJ also, but it's a 2.5 not a 4.0. Excellent around town, decent on the highway (I don't drive over 65-70 in it anyway). 4LO is awesome......
I ran my 5 speed with 4.10's and it was too low for the highway in my opinion. I like to do 80-85 on long trips when the speed limit is 75. 3.55's would be perfect in my opinion for a 5 speed with 31's and it's dirt cheap to get 3.55 axles because they're all over the place and most people don't want them.
I ran my 5 speed with 4.10's and it was too low for the highway in my opinion. I like to do 80-85 on long trips when the speed limit is 75. 3.55's would be perfect in my opinion for a 5 speed with 31's and it's dirt cheap to get 3.55 axles because they're all over the place and most people don't want them.
Nope, not kidding, just personal preference. I now run my 5 speed with 33's and 4.88's because I geared it for the 35's that will be going on next. It's a tad too low for my tastes on the highway. I prefer to gear it for highway and city driving, and then get lower gears in the transfer case for the slow rock crawling. The little extra axle gearing doesn't make enough difference on real technical rock climbs anyways in my opinion, you need way lower gears such as a lower TC ratio.
Everything I've said DOES NOT apply to automatic transmissions though. I've run 235's (29's) with 4.10's and an automatic (AW4) and loved it.
I'm running 32s and a set of 4.11 axles from a junkyard 4-banger. I though t it was a good gearing with the AX-15 (0.79 5th gear) for my daily driver that sees 75 on a regular basis. Now I have an AW4 which has a 0.705 4th gear . The 4.11s are still fine and 4.56 would probably be an improvment. But then again the local pull-n-save salvage yard only charges $50 for used axles and I sold the left over shafts for $125 on eBay.
Hey I have a manual trans with 3.07 gears and 31" tires, it wheels ok but i would like to crawl a bit lower. I also have a 27sp 8.25 axle. Would I notice a gain by swaping in a 29sp 8.25 with 3.55 gears?
I have a buddy here who just asked the more or less the same question, we put it on the calculator, and it returns it to stock performance. 3.55 axles are piled up everywhere, I've got a couple of sets of spare axles here I told him he could have for free. For a little more than a days work, he figure's it's worth it.
