dumb question on regearing

lowgunner · **Posted:** Mon Jan 28, 2013 10:37 pm

I've heard recommendation that one should regear from the KK's 3.7 gears to 4.XX or so once you have installed 31 inch tires. I was looking around the new MOAB addition and it comes with 3.21 or optional 3.73 gears. Does this sound right? I believe it does have 32 inch tires as well.

If this is correct, the gear currently in the KK is adequate for 32 or am I missing something.

Build & Price: 2013 WRANGLER UNLIMITED MOAB EDITION 1 SELECT MODEL

PowertrainPowertrain
6-Speed Manual Transmission $0
Powertrain
5-Speed Automatic Transmission $1,125
$18/month*
Powertrain
3.21 Rear Axle Ratio $0 Powertrain
Engine Block Heater $95
$2/month*
Powertrain
3.73 Rear Axle Ratio $195$3/month*
PackagesPackages
Dual Top Group $1,685
$26/month*

Bmxer524 · **Posted:** Mon Jan 28, 2013 10:53 pm

I think their transmissions are geared differently than the KK's 4speed auto or 6speed manual(might be the same as a JK 6speed, not really sure there).

tommudd · **Posted:** Mon Jan 28, 2013 11:49 pm

Also look at horsepower ratings between the KK and JK ( about 75 more for the JK)
also transmission ratios, vehicle weight etc

Diggerfreek · **Posted:** Tue Jan 29, 2013 2:26 am

A manual KK from the factory came with 3.21's and the Auto equipped KK's came with 3.73's..

If your going to 32's, 4.56's are the only way to go as that brings you back to very close to stock performance. You could run a 31" on the 3.73's but you would loose a lot of power.... 4.10 bring you back to stock.

TurboGoKart · **Posted:** Tue Jan 29, 2013 3:12 am

^^Good info!!

While we're on this topic, does anyone have a link for how to re-gear? I've torn apart a handful of FWD transmissions to replace diff's and whatnot, so I'm not scared to do this myself, I'd just like to look at how to do it before I actually do it. I'd imagine there's some shimming/measuring required and I'm curious as to how to go about that.

lowgunner · **Posted:** Tue Jan 29, 2013 10:29 am

Diggerfreek wrote:

A manual KK from the factory came with 3.21's and the Auto equipped KK's came with 3.73's..

If your going to 32's, 4.56's are the only way to go as that brings you back to very close to stock performance. You could run a 31" on the 3.73's but you would loose a lot of power.... 4.10 bring you back to stock.

Thanks,

Would I just need to order two of these from JBA, for the rear and front diff to do the job?

Product ID: C825456
Product Name: Superior Axle Ring & Pinion
Description: 8.25 Ring and Pinion 4.56
Price: $339.56

tommudd · **Posted:** Tue Jan 29, 2013 10:39 am

lowgunner wrote:

Diggerfreek wrote:

A manual KK from the factory came with 3.21's and the Auto equipped KK's came with 3.73's..

If your going to 32's, 4.56's are the only way to go as that brings you back to very close to stock performance. You could run a 31" on the 3.73's but you would loose a lot of power.... 4.10 bring you back to stock.

Thanks,

Would I just need to order two of these from JBA, for the rear and front diff to do the job?

Product ID: C825456
Product Name: Superior Axle Ring & Pinion
Description: 8.25 Ring and Pinion 4.56
Price: $339.56

Thats fine for the rear,
won't work in the front since its not a 8.25

lowgunner · **Posted:** Tue Jan 29, 2013 3:03 pm

I assume I would need to do both front and rear. What would you suggest for the front?

Ted15 · **Posted:** Wed Jan 30, 2013 6:58 pm

lowgunner wrote:

I assume I would need to do both front and rear. What would you suggest for the front?

Here's a copy of the quote I got from 4WP a couple weeks ago.
   2010 JEEP LIBERTY (KJ) SPORT
EAT912A553                1      1      0      0.00            618.520            T
   CHRY 8.25inTRUETRAC 29SPL C-CLIP 1997UP
EAT912A585                1      1      0      0.00            410.990            T
   D30 TRUETRAC 3.73U 27SPL
G/22-2029-410             1      1      0      0.00            198.941            T
   CHRY 8.25in 4.10 R&P
G/235-2029                1      1      0      0.00             78.392            T
   CHRY 8.25"
ALYD30410RJK              1      1      0      0.00            289.397            T
   D30 REV 4.10 RING/PINION 07-10 JK
G/235-2050           1           1      0      0.00            109.809            T
DANA 30 FRONT JK
SHO4-1025-1               1      1      0    304.00     0.00    14.950            T
INSTALL RING & PINION FRT DANA 28-35 OR EQUIV
OILDISP                                                                     12.50 T
OIL DISPOSAL FEE
SHO4-1026-3               1      1      0    344.00     0.00    17.940            T
INSTALL RING & PINION REAR DANA 44-60 OR EQUIV
OILDISP                                                                     12.50 T
OIL DISPOSAL FEE
OUT                                                                          0.00 T
FREIGHT OUT
This has Detroit tru tracs in the quote. The front takes the same gears as the JK does. They're different from the KJ.

lowgunner · **Posted:** Thu Jan 31, 2013 9:33 pm

Thank you Ted15!

I heard that one should regear all the time due to power issues, but I don't have lack of power, just MPG issues. With the hypertech, KN and some other slight modes, the power is not an issue. It still has pretty good get-up-n-go even with 32 inch tires, but the 12 mpg around town and 15 hwy is what I'm trying to solve.

Now, I just need to have some first hand account on increased mpg before I go and do all this. One thing I'm trying to understand is with the higher gear ratio, I assume that there is more revolution required to perform one tire rotation, ergo, higher rmp relative to each individual tramission gear to turn the new diff gear vs. the stock diff gear.

Can anyone who have regeared let me know of mpg improvements and any other pros vs. con if you had to do it all over again?

tommudd · **Posted:** Thu Jan 31, 2013 10:06 pm

Regearing helps in the MPG department due to getting the engine back to near ( or closer to) stock RPMs . Say you started out with 29 inch tall tires and 3.73 gearing, going to lower gearing with 32s will get it closer to what it was stock ( RPM wise etc. Also since lifted and larger tire/more weight to pull or push around so you need more torque) , lower gearing again will help.
I drove for two weeks with 32s and 3.73s could hardly use overdrive, mileage went down 4-5 MPGs and it ran about 10-12 degrees warmer
after regearing was like I was back to stock tire height ( almost) much better mileage, more power and could use OD
You guys with the KKs are lucky since you can go deeper with the gearing to 4.56s etc.
I'd love to have those with the 32s :wink:

but the 4.10s work for now

Ted15 · **Posted:** Thu Jan 31, 2013 10:15 pm

tommudd wrote:

Regearing helps in the MPG department due to getting the engine back to near ( or closer to) stock RPMs . Say you started out with 29 inch tall tires and 3.73 gearing, going to lower gearing with 32s will get it closer to what it was stock ( RPM wise etc. Also since lifted and larger tire/more weight to pull or push around so you need more torque) , lower gearing again will help.
I drove for two weeks with 32s and 3.73s could hardly use overdrive, mileage went down 4-5 MPGs and it ran about 10-12 degrees warmer
after regearing was like I was back to stock tire height ( almost) much better mileage, more power and could use OD
You guys with the KKs are lucky since you can go deeper with the gearing to 4.56s etc.
I'd love to have those with the 32s :wink:

but the 4.10s work for now

Have you looked at swapping out the axel any more?

lowgunner · **Posted:** Thu Jan 31, 2013 10:23 pm

Well, that does it. Thanks Tommudd. First hand experience with improved mpg. Looks like it's gonna cost about 2 grand at a shop. Gotta start working on the tax return pronto!

Wearyman · **Joined:** Mon Aug 22, 2011 2:01 pm **Posts:** 161

Well I'm feeling stupid again, so I guess I'll ask and try to get edumacated; :mrgreen:

- Is regearing something that the dealership can do, or is this a strictly shadetree/DIY thing we are talking about here?
- When regearing, what exactly are we doing? (I know, My ignorance is showing. Sorry about that.) Are we just changing out the front and rear axle gears, or is this in the tranny itself?
- Are there Chrysler made parts specifically for this, (IE: a low gear kit for the KK or using the gearing from a Wrangler) Or is it a strictly aftermarket affair?

I'm looking to do my OME lift this spring along with a new set of shoes (probably either Duratracs or Treadwright Guard Dogs) and the cost and complexity of regearing is going to factor in whether I go 245/75R16 or 265/75R16. I don't think I will need to regear with the 245s as they are only 30s, not enough size difference to matter. but the 265s are 32s, so I will absolutely have to regear.

If it's too expensive to do all that at once I'll stick with the slightly smaller tire for now and look to upgrade in a year or two. If it's not too bad (a couple hundred extra) then I'll just go all in for the beefy tires and rock some Phat rubber. :mrgreen:

tommudd · **Posted:** Fri Feb 01, 2013 1:12 am

regearing is not a shadetree type of modification
unless you have a heck of a well equipped tree in your yard
dealers/ 4 wheel drive shops / etc that do gears can do it
Has nothing to do with the transmission only changing the gears in the front and rear diffs
Its not a two hundred dollar mod, gears / bearings etc for one end is more than that

Wearyman · **Joined:** Mon Aug 22, 2011 2:01 pm **Posts:** 161

tommudd wrote:

regearing is not a shadetree type of modification
unless you have a heck of a well equipped tree in your yard
dealers/ 4 wheel drive shops / etc that do gears can do it
Has nothing to do with the transmission only changing the gears in the front and rear diffs
Its not a two hundred dollar mod, gears / bearings etc for one end is more than that

Thanks Tommudd. I guess I'll just stick with the 245 size tires then as I will already be spending quite a bit between them and the OME lift this spring. Maybe in a couple years I can go bigger. Thanks!

dumb question on regearing

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