Regear question

JeepNCrowd · **Posted:** Wed Mar 19, 2014 8:49 pm

Why is it we have to re-gear to run 32"s when, many JKs can get away with 33"s and 35"s with out re-gearing?
We both have 3:73 Diff gears (sahara/x/sport) and V6 engines. We both can have 29" stock tires (X/ Sport).

tommudd · **Posted:** Wed Mar 19, 2014 8:56 pm

JeepNCrowd wrote:

Why is it we have to re-gear to run 32"s when, many JKs can get away with 33"s and 35"s with out re-gearing?
We both have 3:73 Diff gears (sahara/x/sport) and V6 engines. We both can have 29" stock tires (X/ Sport).

For one thing different engines and for another lots of people do it right and do regear. Only the mall runners don't and then complain about poor mileage
Have you ever ridden in a JK with 33s or 35s?? Can you say D O G !!???

JeepNCrowd · **Posted:** Wed Mar 19, 2014 9:03 pm

Ok so they fo feel it. I know in my club they start you can run 35"s on a JK and it's tolerable, but its better when reheated. They still hit the rocks though. I guess it just rocks me off we have to reheat to run 32"s.

So is anyone running 32"s that hasn't regeared yet?

tommudd · **Posted:** Wed Mar 19, 2014 9:14 pm

I ran for a couple of weeks with 3.73s and 32s
Couldn't run overdrive at all even on level straight roads, it sucked
Mileage went from 20 to 15, ran hotter,
From where I live to my buddies was about 75 miles on the Interstate. Even with 265-70s and stock gearing it would downshift at least 25 times on small hills. After the 32s and regearing it would go the whole way and never downshift
Several have regeared and they're running 245-75-16s and 255-70-16s with great results

Actually I wish KJs could go to 4.56s since it would be great with 32s. 4.10s would be good for 245-75-16s.

JeepNCrowd · **Posted:** Wed Mar 19, 2014 9:38 pm

Im trying to hold off on re-gearing since I have something "special" planned for my KK in about 2 years. :twisted:

But I may have come across a good deal on 32" tires on wheels I want.

tommudd · **Posted:** Wed Mar 19, 2014 9:54 pm

Personally I wouldn't run for even a few months without regearing. The extra wear and tear on the motor and transmission is not worth it .

HedsIc · **Posted:** Wed Mar 19, 2014 11:22 pm

That's my problem. I just feel like the 245/75's I have are to small. Would like at least 265's but like Tom said. Extra work on the motor/tranny not worth the risk until without the regear.

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streetglideok · **Posted:** Thu Mar 20, 2014 9:39 pm

JeepNCrowd wrote:

Why is it we have to re-gear to run 32"s when, many JKs can get away with 33"s and 35"s with out re-gearing?
We both have 3:73 Diff gears (sahara/x/sport) and V6 engines. We both can have 29" stock tires (X/ Sport).

Don't let them fool you. Some KJ owners claim they don't feel any power loss with 31"s as well. Just the small tire size increase I did, I felt it immediately. Granted, in 4lo, you likely wouldn't notice it as much. But on the road in 2hi you will. Just remember, if you go to regear, if you are running open diffs, upgrade to lockers or LSDs. It's already apart.

Cherrie 274 · **Posted:** Fri Mar 21, 2014 10:21 am

Another post disappeared.
So I'll try again.Re think bigger is better.
A 2 inch increase in tire size only gives you 1 inch.
I need to go thru things more than over. Snow and mud.Spend money on bigger tires then regear and still have loss of power. Locked or LS and no loss in power no regearing.
A few years ago at the Jeep Blessing a stock looking wrangler with older couple in front and 2 others in back, was the first to clear the mud pit. When the purple Jeep pulled up people laughed, and booed. I figured the purple Jeep was there to have fun or knew something we didn't.
Yep locked. EPIC.

tommudd · **Posted:** Fri Mar 21, 2014 2:54 pm

JeepNCrowd wrote:

Why is it we have to re-gear to run 32"s when, many JKs can get away with 33"s and 35"s with out re-gearing?
We both have 3:73 Diff gears (sahara/x/sport) and V6 engines. We both can have 29" stock tires (X/ Sport).

To get us back on track the OPs original question

JeepMorrison · **Joined:** Thu Jul 16, 2009 11:34 am **Posts:** 1236

Here's my experience with 245/75r16.....
I have noticed some power loss. It dosent shift crazy but im in the costal flats of southeast Texas. My fuel milage is around 17-18mpg during my last trip going 70-75. No over heating and no weird shifting. 1900rpm at 65mph at 24ft above sea level.

Now....32s and 3.73s. I have put street tires on it. Didnt run much due to lift required. But noticeable power loss and rpm was 1800 at 65mph. Didnt drive it much to see shifting weird.

But even with 245/75 the KJ would be better with 4.10. Is it doable with 3.73, yeah sure, but theres better way. Now 32s would need to be regeared to 4.10 at least to feel like it isnt a slug. Im sure it will do fine at my location but up north with hills, no way

Sent with the power of children's screams!!!

lfhoward · **Posted:** Fri Mar 21, 2014 9:37 pm

4x4kayak2112, my experience is just as you describe. I have 245/75/16's and stock 3.73 gears. Ok on the flat coastal plain, but once I drive into the foothills or mountains it's shifting all over the place and can't seem to find a sweet spot. I'm sure it's not good for the tranny in the long run, and the gas mileage really takes a hit. I plan to upgrade to 4.10's once I can save up the cash.

Bmxer524 · **Posted:** Sat Mar 22, 2014 3:22 am

All has to do with the engine, its power band, transmission and gearing. Clearly, our 3.7s are meant to rev. Around 2k or so is the sweet spot for cruising. Our 4 speeds are designed to keep us there. At 40 mph I'm sitting around 2k, maybe a little higher. My friend just bought a 2014 JKU, 3.6, 5speed auto and 3.21 gears. The new 3.6s have a completely different power band, so the gears are of course different. 40mph, and he cruises around 1200-1500rpm. If we ever ran that low we start bogging. Hell, I even feel it when I hit OD at 50mph. We lug that low lol. Of course, if he had the optional 3.73 or Rubicon 4.10s, he would be higher at those speeds, but could have the chance to use his other gears, or sit higher in the power band.

WHITE the civilian · **Posted:** Wed Apr 09, 2014 1:51 am

I will be running 235/85's in a few months and want to get those factory MPG's back. Do I NEED a steel front diff to run 4.56 Gears?

Bmxer524 · **Posted:** Wed Apr 09, 2014 2:18 am

WHITE the civilian wrote:

I will be running 235/85's in a few months and want to get those factory MPG's back. Do I NEED a steel front diff to run 4.56 Gears?

I believe so. I don't think they make 4.56s for a stock KJ front.

tommudd · **Posted:** Wed Apr 09, 2014 6:09 am

WHITE the civilian wrote:

I will be running 235/85's in a few months and want to get those factory MPG's back. Do I NEED a steel front diff to run 4.56 Gears?

Yes to run 4.56s you need the steel front diff

Chipppy · **Joined:** Wed Apr 11, 2012 5:23 pm **Posts:** 223

JeepNCrowd wrote:

Ok so they fo feel it. I know in my club they start you can run 35"s on a JK and it's tolerable, but its better when reheated. They still hit the rocks though. I guess it just rocks me off we have to reheat to run 32"s.

So is anyone running 32"s that hasn't regeared yet?

I am running 265/75/16's without a regear. It isn't the way to go. I always have o/d off and she is still a dog. I do have an 02 so my first gear or so is a bit lower. YOU WANT A REGEAR FOR 265's!!!! I regret not running 255's or 245's. My father owns the jeep yet i put the money for aftermarket parts and later I will get the jeep. I have tried to convince him about the regear but he thinks it's the dumbest thing ever because I bought the jeep for 5500 and putting another 1000 dollars or so into it on top of my 1400 in other parts. Long story short when you want 265's add a locker/limited slip gears and bearing to the price tag. I should have.

JeepNCrowd · **Posted:** Thu Apr 17, 2014 7:53 am

Perhaps the 235/85/R16 will be a friendlier 32 to go with. I know I should still re-gear with them, and if I wasn't planning on replacing the diffs in a couple of years I would, but I'd imagine it wouldn't be as bad as the 265's. It's a lighter tire with less rolling resistance. Again I know re-gearing is recommended, but how much do you better do y'all think the 235's are vs 265's on stock gearing?

tjkj2002 · **Posted:** Thu Apr 17, 2014 9:51 am

JeepNCrowd wrote:

Perhaps the 235/85/R16 will be a friendlier 32 to go with. I know I should still re-gear with them, and if I wasn't planning on replacing the diffs in a couple of years I would, but I'd imagine it wouldn't be as bad as the 265's. It's a lighter tire with less rolling resistance. Again I know re-gearing is recommended, but how much do you better do y'all think the 235's are vs 265's on stock gearing?

235/85's are maybe a few lbs lighter then a 265/75 but the 235/85 is actually slightly taller then a 265/75.Either tire will cause the same power robbing effect.

I used specs for a MT/R K..............

235/85 = 50lbs and is 32" tall on a 6.5" rim

265/75 = 52lbs and is 31.9" tall on a 7.5" rim

lfhoward · **Posted:** Thu Apr 17, 2014 2:59 pm

I just saw a lifted X-Terra with 315-75-R16's on it during my lunch break. Sure hope he regeared!

Regear question

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