I've heard that the stock auto trans & axles were designed to accept bigger wheel and tire packages, and I've also heard that you can't run bigger tires like that without beefing up the drivetrain. Obviously you'd have to do it for off-roading, but with a mill like the 4.0, what's the wear & tear going to be day-to-day street and highway driving? Thanks for your insight.
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fat 31's too taxing on a stock A/T?
- Thread starter Skylar
- Start date
oo7ravisXJ
NAXJA Forum User
- Location
- San Ramon, Nor-Cal
Not a big deal. Not that i endorse it, but i've been on 33's and DDrove it and wheeled it for a year now with no problems. Mine does have a tranny cooler which may help, but with 31's i really wouldn't sweat it.
oo7ravisXJ
NAXJA Forum User
- Location
- San Ramon, Nor-Cal
na, these things will take a beating, are you planning on regearing? Some say with 31's its a must, but like i said, im on 33's with stock gears and its fine, i just drive slow. That being said, 33's and stock gears are defiantly not ideal, plannin 4.56's once i get the money...
I'd regear if I planned to mud it or rock it. As it is I'll do light trail duty like camping, and rip through this michigan snow when it's on the ground every year. I can't see going up from 31's, because I only plan to do a 3" lift, I think it'll ride nice. Like you I drive slow. I think I'll do a throttlebody and intake, but not for speed's sake.
PurpleCherokee
NAXJA Forum User
- Location
- MO
I ran 31's for two years as a DD with never a problem with power, or powertrain. In fact, with a few bolt-ons, you can almost get your jeep back to stock acceleration. You're speedo'll be off by roughly 11% or so depending on what kind of 31" you get. The only reason I brought my jeep back to stock suspension was because I was getting horrible death wobble and didn't have the money to do the proper front end suspension work to make it stop without rebalancing my mud-terrains EVERYDAY lol. And I've seen first hand what an MJ on 35's can do with a completely stock drivetrain. It got the piss drivin out of it off the road with NEVER a problem. 31's... no big deal at all as long as you have a good lift kit.
91Woody
NAXJA Forum User
- Location
- Manchester, NH
If you are talking about 31x10.5x15 you will be okay. I ran 31's on stock drivetrain and gears for the last year and putting on 15K miles. I had zero issues, but there will be guys who have re-geared and will tell you to wait and regear due to the differences.
I had my trans serviced, changed the rear diff oil and everything looked and smelled normal- no evidence of excessive wear.
I had my trans serviced, changed the rear diff oil and everything looked and smelled normal- no evidence of excessive wear.
rogersjeep
NAXJA Forum User
- Location
- Pearland Texas
I've ran 31"s for about a year with 180xxx on clock and had no issues. Now I've gone up to 32"s and still have had no ill effects it'll still bark the tires from a stand still.
96 2 door 4.0 auto 3:55 open both ends cold air intake and header
96 2 door 4.0 auto 3:55 open both ends cold air intake and header
xthejuicex
NAXJA Forum User
- Location
- CNY
Ive ran 33x12.5 on 15x10 steels on stock gearing and I havent had any real problems. Acceleration is not as good obviously but my heep can still out acceleration compact cars lol. Also braking suffers but that is also expected. Running 31"s should be fine.
jeepboy381
NAXJA Forum User
- Location
- Gresham, Or
Running 31's on stock gears won't hurt anything but your wallet. Expect a big drop in gas mileage, in my 2000 I went from 16-20 and am now getting 13-15 mpg. It is noticabley slower and I believe it really needs 4.10 gears. It still is pretty quick but not like it used to be before the bigger tires. If anyone tells you that you will still get good mileage don't listen to them, gears are necessary to do it right. I am getting 4.10s soon!
MoparManiac
NAXJA Forum User
- Location
- Amherst, NH
Yeah 31s and stock gearing isn't ideal, but definitely driveable.
I had it on my old 91 2-dr and it drove around decently. Highway suffers the most, as its hard to keep up the speed going up hills.
Mpg = about 15. No matter what. Floor it, 15. Baby it, 15. Don't expect miracles.
Regear when you can afford it, and get rear disc when you can. Definitely two of the most worthwhile upgrades.
I had it on my old 91 2-dr and it drove around decently. Highway suffers the most, as its hard to keep up the speed going up hills.
Mpg = about 15. No matter what. Floor it, 15. Baby it, 15. Don't expect miracles.
Regear when you can afford it, and get rear disc when you can. Definitely two of the most worthwhile upgrades.
Thanks for all the replies. When I get the money I'll be popping for a lift, and I'll work on the drivetrain after that. I bought the jeep it came on pretty much new tires with 15" allied rockcrawlers. The metal and rubber alone makes up the bulk of what I paid for the whole vehicle, I couldn't pass on it. The P.O. cut me what I consider a once in a lifetime deal because I worked really hard for the money I saved. I was thinking 31" BFGs when these wear out, which won't be anytime soon.
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