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Unread 03-30-2012, 07:32 AM   #1
JcArnold
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JKU 5.13/automatic/33" tires, gear question

Ive got a JKU with 33" nittos and an automatic with 3.73. I just scored a serious deal a a set of 5.13 gears. I want to know from people running this setup how they like it. Pros and cons.

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Unread 03-30-2012, 10:13 AM   #2
yellowjp79
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In my personal opinion 5.13 are too low for the 33's. I think 37's would be great for the 5.13. But opinions are like *** holes, everybody has one so take it for what its worth.
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Unread 03-30-2012, 10:24 AM   #3
JcArnold
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I've read a lot of write ups about this but most involve the manual transmission to which I would agree 5.13's and 37s but the auto seems to get different reviews but I still haven't seen anyone reply that actually has this setup. That's what I'm hoping for here. I have a set of 35's I can run if it's too low but then I've read you need 5.38's for those with the auto. So I would wind up back in my original situation.
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1990 YJ Islander without the Island so I guess that makes it just an " er "
2010 JKU Sahara Super Lift 4", 33" Nitto Mud Grapplers, Custom Front bumper and rocker protection-SOLD
2012 Jeep JKU MW3 Edition Rubicon



37x12.50x17 Goodyear Wrangler MTRs
Pro-Comp 7031 17x9
Rock Krawler 5.5" X-Factor
Fox Racing Shocks
Synergy Front Cage Kit
Synergy Axle Tubes/C gussets
4.88 gears frt/rr
Replacement frt/rr driveshafts
Poison Spyder rockers
And a bunch of other little stuffs
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Unread 03-30-2012, 10:28 AM   #4
WXman
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I went from 3.73 to 4.88 instead of 5.13. I think it's perfect. 70MPH puts me at 2,500RPM which is a little high, but still in the "green zone" on the guage. It has enough guts to actually hold overdrive on hills now, unless I'm driving into a head wind. I like it a LOT.

Cons: been chasing driveline vibration ever since the install. I think it's the driveshaft(s) but not 100% certain and I'm now having to purchase shafts to chase these vibes. You can't open one can of worms on these JKs without opening another. Once you do a mod...it just becomes a snowball effect.

Pros: 1st gear is great offroad. Reverse is actually usable now. I can back my trailer into the driveway without the TC shuddering and slipping. I can hold OD on the highway. Better driveability.

If I could do it over again, I'd have never touched the gears. I'd have stuck to 32s which are available in "P" and "C" ratings to save weight and not need gears. I would give up the 0.5" of ground clearance to gain keeping my factory warranty and not having to chase vibrations.
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Unread 03-30-2012, 10:39 AM   #5
JcArnold
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thats strange that you would get a vibration from a gear change unless your pinion isnt true and creates a slight wobble. 4.88 to 5.13 isnt that much of a difference but it may be enough. I just hated to pass up 5.13's with install kits for $400. My fuel economy took a nose dive when I changed to 33's and I can forget about OD for the most part. Thanks for your input
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1990 YJ Islander without the Island so I guess that makes it just an " er "
2010 JKU Sahara Super Lift 4", 33" Nitto Mud Grapplers, Custom Front bumper and rocker protection-SOLD
2012 Jeep JKU MW3 Edition Rubicon



37x12.50x17 Goodyear Wrangler MTRs
Pro-Comp 7031 17x9
Rock Krawler 5.5" X-Factor
Fox Racing Shocks
Synergy Front Cage Kit
Synergy Axle Tubes/C gussets
4.88 gears frt/rr
Replacement frt/rr driveshafts
Poison Spyder rockers
And a bunch of other little stuffs
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Unread 03-30-2012, 11:25 AM   #6
jrmars07
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I have 33's and 4.88's and I am over geared... I recommend staying away from 5.13's with a D30 anyway if you are doing hard wheeling. Pinion gets way to small... Get 4.56's if 33's is the biggest you will ever go. Get 4.88's if you plan on going to 35's at some point. If you are going bigger than 35's time to really build up the front axle or get a new one.
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Unread 03-30-2012, 09:20 PM   #7
Prot
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I have 5.13's, automatic, and 35's. Yes I have a Sahara which means D30 upfront. The gear ratio is perfect and no vibrations. WXMAN did his own gear install and reused a lot of parts and has been chasing vibes ever since. I and many others left the complexity of regearing to a shop that specializes in it and have gotten good results with no vibration, but with the negative effect of a lighter wallet.

JK's have been around long enough that there is a good knowledge base now with numerous threads. 2012's are obviously different due to different engine and transmission.

So, here it is for automatic:

32"...4.56
33"...4.88
35"...5.13
37"...beefy axles and 5.38

And of course for you manual guys:

32"...4.10
33"...4.56
35"....4.88
37"....5.13

In a JK D30, you can go to 5.13 without a problem.

If you have a 2012 or newer, these numbers are probably wrong.
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Unread 03-31-2012, 09:01 AM   #8
JcArnold
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Thanks Prot for the post. That makes sense.
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1990 YJ Islander without the Island so I guess that makes it just an " er "
2010 JKU Sahara Super Lift 4", 33" Nitto Mud Grapplers, Custom Front bumper and rocker protection-SOLD
2012 Jeep JKU MW3 Edition Rubicon



37x12.50x17 Goodyear Wrangler MTRs
Pro-Comp 7031 17x9
Rock Krawler 5.5" X-Factor
Fox Racing Shocks
Synergy Front Cage Kit
Synergy Axle Tubes/C gussets
4.88 gears frt/rr
Replacement frt/rr driveshafts
Poison Spyder rockers
And a bunch of other little stuffs
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Unread 01-13-2013, 03:13 PM   #9
MigueloP
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Bringing back this old threat...how is the 33" with 4.88 and Auto transmission?
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Unread 01-13-2013, 03:18 PM   #10
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Quote:
Originally Posted by Prot View Post
I
So, here it is for automatic:

32"...4.56
33"...4.88
35"...5.13
37"...beefy axles and 5.38

In a JK D30, you can go to 5.13 without a problem.

If you have a 2012 or newer, these numbers are probably wrong.

5.13's and an auto are better suited to 35's. 5.13 is the lowest you can go with your axle unless you have a Rubicon, then you can go to 5.38's (if going to 37's...which opens a whole new can of worms).

Go ahead and install the 5.13's now and install 35's later. Mean time, you'll be burning rubber off every stop sign. LOL

OR...just sell the 5.13 gears for a profit, buy some 4.56 gears and you'll be sitting pretty.
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Unread 01-13-2013, 05:00 PM   #11
MigueloP
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Yes, but i have 33" (truthly 33"), its a JKU Auto Sahara, im deciding to go with 4.88 or 5.13. The difference in the gear chart is just 120 rmps, no to much. I live in a 1800 feet high area, not fan of rockcrawling, more like expedition vehicle, but also its my DD.

I dont know now if, in the future, im going to move over 33" since my tires are brand new.

What do you recommend?
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Unread 01-13-2013, 06:05 PM   #12
HappyTrails
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Quote:
Originally Posted by MigueloP View Post
Yes, but i have 33" (truthly 33"), its a JKU Auto Sahara, im deciding to go with 4.88 or 5.13. The difference in the gear chart is just 120 rmps, no to much. I live in a 1800 feet high area, not fan of rockcrawling, more like expedition vehicle, but also its my DD.

I dont know now if, in the future, im going to move over 33" since my tires are brand new.

What do you recommend?
Sell the 5.13's and buy some 4.56 gears, at most 4.88 gears (if you tow).
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Unread 01-13-2013, 06:31 PM   #13
MigueloP
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Really?, 4.56??, there seems not so much difference from 3.73 and 4.56, i wouldnt even consider 4.56
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Unread 01-13-2013, 08:30 PM   #14
JIMBOX
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This is always interesting, comments by graph readers !

I've been running 5.38s/33.6" Hankook Dynapros for almost two years and My performance is up 50% and my gas mileage is up 15/20%-

With a pre 2012 auto, 5.13/5.38s are great for ANY TIRE LARGER THAN 32" -

If you tow and keep 33" tires and notta Rubi--get 5.13s, it'll be great

JIMBO
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Unread 01-13-2013, 08:40 PM   #15
MigueloP
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I dont tow anything...but i think 5.13 are the way to go, do you think the jeep will behave ok as a daily driver with that setup?

What about the small pinion and ring problem?
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