Lifted KKs with 31 inch tires - did you regear?

Tx_roadie · **Joined:** Sat Aug 10, 2013 10:57 pm **Posts:** 17

Hi all. So I'm in the final planning phases to lift my 2010 KK - TomMudd 3.5 lift, and planning on ~31 inch BFG AT/KO (actual diameter 30.6 inches). I may be wrong, but that tire diameter is about the threshold to NOT have to regear? 32 inch - definitely, but my understanding is I'll be fine with 31 inches to not regear? Also - for those who run ~31 inch tire diameter, any power/pickup/performance issues?

I'm coming from an older XJ with 3.5 inch lift and same ~31 inch BFG AT/KO - didn't regear, and basically drives well; maybe 1 city/2 hwy drop in MPG, still have good low end power, questionable tranny temp increase (but only started to notice 4-5 years after my lift, and it's a '94 XJ, so nearing the end of her days...)

tommudd · **Posted:** Wed Oct 23, 2013 10:57 am

There is no magical number that say at running a 30 inch tall tire you don't have to but at 31 you do.
You will notice a power loss, less fuel mileage etc with any tire above stock height.
But most get along with the conventional 245-75-16 size range and put up with the loss of power and mileage. Not only does the extra height get you but also the extra weight associated with the tires, extra skids etc.
Most recently Ted15 regeared and I know he likes the power he got back after regearing
So bottom line is personally if I was going to a 30-31 I'd look into regearing in the near future.

lfhoward · **Posted:** Wed Oct 23, 2013 11:03 am

I notice a loss in MPG and power, most notably in the city and on highways with hills. On the flat going 65 I can average about 19-20 MPG, but with hills it is more like 16-17. Stock I routinely got 22-23 on the highway. In the city I get about 12-13 MPG, compared to stock 14-15. I am wanting to regear to 4.10's and add limited slip TrueTracs, but don't have the :2cents:

for it yet. In the meantime the ride is not too terribly bad, so I can definitely put up with it, but hearing what Ted15 says about how fun his is to drive, I am really looking forward to the regear.

jjohnson1892 · **Posted:** Wed Oct 23, 2013 11:22 am

I run 245/70/16's which is about the same diameter as what you're looking to add. I didn't regear, but I also didn't notice a huge power loss or MPG loss. I'm not overly concerned with MPG loss, but definitely am into how fun driving can be and mine is still quick and a good time to take on backroads. It should be noted that I still haven't installed skids on mine (which I plan to do in the near future) so that could be a pretty big factor.

KKomodo · **Posted:** Wed Oct 23, 2013 11:34 am

I bought mine with 245/75r16 with no lift and never had any issuea. I get way better mileage and power than my mother-in-laws jk. I have drove a few stock 2wd kk's through work and I'd take mine over thiers any day. Now with the lift on top of my k&n, exhaust, lift and spacers I could still outrun any other kk around my town on/off road. Next will be mt's and a programmer and yes 4.10's hopefully after the kid.

tommudd · **Posted:** Wed Oct 23, 2013 11:56 am

jjohnson1892 wrote:

I run 245/70/16's which is about the same diameter as what you're looking to add. I didn't regear, but I also didn't notice a huge power loss or MPG loss. I'm not overly concerned with MPG loss, but definitely am into how fun driving can be and mine is still quick and a good time to take on backroads. It should be noted that I still haven't installed skids on mine (which I plan to do in the near future) so that could be a pretty big factor.

245-70-16 is only 29.5 or so h's talking about a 31 inch tall tire
there is a difference even though 1.5 inches overall but its the break over to needing to and just running a little more than stock size tire

jjohnson1892 · **Posted:** Wed Oct 23, 2013 12:02 pm

tommudd wrote:

jjohnson1892 wrote:

I run 245/70/16's which is about the same diameter as what you're looking to add. I didn't regear, but I also didn't notice a huge power loss or MPG loss. I'm not overly concerned with MPG loss, but definitely am into how fun driving can be and mine is still quick and a good time to take on backroads. It should be noted that I still haven't installed skids on mine (which I plan to do in the near future) so that could be a pretty big factor.

245-70-16 is only 29.5 or so h's talking about a 31 inch tall tire
there is a difference even though 1.5 inches overall but its the break over to needing to and just running a little more than stock size tire

Bad math

Bmxer524 · **Posted:** Wed Oct 23, 2013 2:27 pm

I notice the larger tires. Do I need to regear? No, but I'm honestly contemplating it. It's not too bad, just don't expect to be a racecar or to accelerate on big hills. Depending on my speed, normally 75-80mph on some overpasses here, she kicks down when on cruise control. It's not every time, but I do notice it.

Tx_roadie · **Joined:** Sat Aug 10, 2013 10:57 pm **Posts:** 17

Thanks all for the input - it's really helpful and given me some things to consider. As it stands, I'll stick with the stock gearing for now, and see how she behaves with the lift/tires. She's not my daily driver, and will mainly be used as a weekender/trail vehicle, so I have time to see how she reacts to the given situations.

Thanks again.

carlosburitica · **Joined:** Sat Jan 05, 2013 1:07 pm **Posts:** 309

i am running 31" km2 on 17" wheels. dont really feel a need to regear.
average is 15mpg
live in florida and is flat.

Ted15 · **Posted:** Wed Oct 23, 2013 4:55 pm

I have 4.10's with 245/75-16 General AT2's. Right around 30" I think. About 3" or so of lift. The power is through the roof compared to stock and I plan to replace these tires with 31x10.5x15's when these wear out. 9.5" would probably be better but the tires I want don't come in that size. I get about 15 mpg, sometimes. I was getting 13 and my KK was completely gutless before I regeared. Had I planned on 32" tires I would've gone with 4.56 gears but I think 31's should do.
I'd like to get a hypertech max energy and a larger throttle body in the future. That should make up for any short commings powerwise.
That said, regear, you won't regret it. The best advise I could give is to find a TRUSTED shop to do the job. Don't think that just because the company has a good reputation that the shop you go to and the technician that you get will be anything like the rest of the company. Trust me, I found out the hard way. Honestly, I could've done at least as good a job as the guy that did mine the first time.

WhiteRider · **Posted:** Thu Oct 24, 2013 10:25 pm

Haven't re-geared yet, but will be as soon as Christmas has passed. I'm probably running a little different set-up than most I have seen on Lost, due to the fact I am also still riding on the 18's with BFG A/T KO's 265/65's

The only thing that I have found to be a bother, is the ESP periodically activating when it shouldn't. Don't know if it is true, but I was told you can put the computer into a "learn mode" and that will fix it, but hasn't bothered me enough to go to the dealership and get it done.

I didn't buy the KK expecting to change a whole lot in terms of mileage the giant "shoebox" could get. Although, I found adding the CAI and upgrading the throttle body did seem to make a noticeable difference when I was highway driving, it was only marginally better in the city. As soon as I lifted and got the bigger, heavier tires - definitely hurt the power off the start, and it doesn't like hills without really making the transmission work. But I'm as much to blame as the lift and tires, as I cannot drive behind anybody for very long!

The trade off in "capability" though, I still feel was more than worth it, as continues to amaze me every time I go wheelin at what it can do. I get asked about it constantly, even the 6"+ Lifted drivers show interest in it.

Long story short, if you want to go BIG, start a "KK Trust Fund" cause if you aren't gonna spend the cash on a re-gear, and other fun stuff - you are gonna need it for gas anyhow.

lfhoward · **Posted:** Sat Oct 26, 2013 12:22 pm

You have a very nice KK, WhiteRider. :JEEPIN:

WhiteRider · **Posted:** Sat Oct 26, 2013 7:02 pm

lfhoward wrote:

You have a very nice KK, WhiteRider. :JEEPIN:

Thanks lfhoward, it's been a fun project for sure. I learned a lot in the process, and gained quite a bit of mechanical confidence - knowing that I did all the upgrades myself.

I couldn't stand to spend a bunch of money making it a better, more capable, nicer looking vehicle - only to take photos of it parked on the street or in the lot. Such a waste of time and money trying to "look cool", when you aren't brave enough to get 'er in tha muck and actually have some fun. Life's too short!

...and we wonder why the KJ/KK get such a bad rap with the rest of the "Jeep community"?

mredmond · **Posted:** Wed Oct 30, 2013 5:11 pm

Ted15 wrote:

...Had I planned on 32" tires I would've gone with 4.56 gears but I think 31's should do...

That said, regear, you won't regret it. The best advise I could give is to find a TRUSTED shop to do the job. Don't think that just because the company has a good reputation that the shop you go to and the technician that you get will be anything like the rest of the company. Trust me, I found out the hard way. Honestly, I could've done at least as good a job as the guy that did mine the first time.

I am looking at regearing now because I can't stand the power loss, and I've also considered moving up to 32s in the future, but that would be a ways off. I don't want to regear twice, so now I'm trying to decide to go with 4.10 or 4.56 in case I get a better lift and bigger tires in the future. What would it be like running 245/75r16s or 31s with 4.56 gears?

Also, what happened the first time they regeared for you?

itsdavem · **Posted:** Mon Nov 04, 2013 12:16 am

Stock 3.73 gears avg 17-18 hwy 245/75r16 2.5 lift
Runs hot going through the mountains

TrueTexUSN · **Joined:** Thu Jun 13, 2013 11:15 pm **Posts:** 104

We (02-12 Libertys) all have the same 8.25 and Dana 30 diffs correct? Would ring and pinion sets for one work for the other? (02-05 Libby's into a 2009?)

tommudd · **Posted:** Tue Nov 12, 2013 3:20 pm

TrueTexUSN wrote:

We (02-12 Libertys) all have the same 8.25 and Dana 30 diffs correct? Would ring and pinion sets for one work for the other? (02-05 Libby's into a 2009?)

rear yes, all except a very very few 02s have the 8.25 rear
front no
08-12 have a different 30 front diff which is basically the same as what comes in a JK 30
02-07s have a D30a which is an oddball set of gears really only made by Dana-Spicer ( reason why I have two extra sets stored away :wink:

)

TrueTexUSN · **Joined:** Thu Jun 13, 2013 11:15 pm **Posts:** 104

tommudd wrote:

TrueTexUSN wrote:

We (02-12 Libertys) all have the same 8.25 and Dana 30 diffs correct? Would ring and pinion sets for one work for the other? (02-05 Libby's into a 2009?)

rear yes, all except a very very few 02s have the 8.25 rear
front no
08-12 have a different 30 front diff which is basically the same as what comes in a JK 30
02-07s have a D30a which is an oddball set of gears really only made by Dana-Spicer ( reason why I have two extra sets stored away :wink:

)

http://www.ebay.com/itm/261323106487?ss ... 1431.l2649

I think I made a boo-boo. This one is for a 02-05 Liberty Dana 30, but it doesn't say a Dana 30a. Need to stay of eBay when I am tired; might have something to sell soon, haha :ROTFL:

tommudd · **Posted:** Tue Nov 12, 2013 9:03 pm

TrueTexUSN wrote:

tommudd wrote:

TrueTexUSN wrote:

We (02-12 Libertys) all have the same 8.25 and Dana 30 diffs correct? Would ring and pinion sets for one work for the other? (02-05 Libby's into a 2009?)

rear yes, all except a very very few 02s have the 8.25 rear
front no
08-12 have a different 30 front diff which is basically the same as what comes in a JK 30
02-07s have a D30a which is an oddball set of gears really only made by Dana-Spicer ( reason why I have two extra sets stored away :wink:

)

http://www.ebay.com/itm/261323106487?ss ... 1431.l2649

I think I made a boo-boo. This one is for a 02-05 Liberty Dana 30, but it doesn't say a Dana 30a. Need to stay of eBay when I am tired; might have something to sell soon, haha :ROTFL:

Actually those will not even fit a KJ
they will fit older XJs though ( the low pinion models)

Lifted KKs with 31 inch tires - did you regear?

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