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-   -   Calling all Re-Geared 3.8L Autos! (http://www.wranglerforum.com/f274/calling-all-re-geared-3-8l-autos-249422.html)

brendan614 06-14-2013 09:53 PM

Calling all Re-Geared 3.8L Autos!
 
I'm going to re-gear very soon. I'd like for all you auto guys (and girls) to tell me what gears you're running and what your tire size is. If you're happy or not. Maybe you wish you went deeper or maybe you wish you didn't go as deep as you did.

I'm running 3.73s with 295/70R17 (33.5") Nitto Trail Grapplers on my stock Moabs. At 70 MPH I'm at about 1750 RPM. She's constantly in and out of OD when I set the cruise. It's bearable if I drive her by foot cause I know how to feather the accelerator.

My mods include a Dynomax cat-back exhaust, a K&N CAI and a Superchips Flashpaq. I will soon add a Viper TB which I have on order. I have a D30 front axel and D44 rear axel.

Everyone I talk to has a different opinion. 4.88s, 5.13s. Some guys even suggested 5.38s.

Before anyone posts the gear selection chart, I've already seen it. I'm looking for real world experience and honest opinions.

Thanks in advance! Sláinte!

rics1997 06-14-2013 11:01 PM

I am running 4.88 with 35 MTR's. I started with 3.73's myself. I know many on here pushed 5.13 when I was getting mine but the shop I used said you really should get the 4.88 unless going to 37's in the future and I am glad I took their advise. I was running 33 Duratrac (32.5) and I really wasn't a fan when on the highway. The rpm's were pretty high at 75mph on the highway and at that speed I was getting less gas mileage then in the City. I moved up to 35's and happy with the combo. I get great get up and go and better highway rpm at around 2500rpm's at 75. I think those that push 5.13's are JKU's. The heavier 4dr might need the extra push but with my 2dr I like the 4.88's better

That's my opinion though from the way mine runs

JKralph 06-14-2013 11:16 PM

I have a very similar experience to rics.

I drive a 2dr 2010, and I regeared not too long ago to 4.88. I'm currently running 33" duratracs, and at 70 mph I'm turning just about 3000 rpm, which is a bit high IMO, but I plan on 35s in the future, so I'm not too worried about it (particularly now that I've read rics post :D).

I would not have gone deeper than 4.88, and I had considered 4.56 for a while, and I'm sure either is fine. 4.56 would have been my choice if I wanted to stick with 33's.

I've only had one chance to wheel it since regearing, but it was night and day. Then again, I was moving from 3.21's to 4.88's, so that could have something to do with it.

Overall, very happy with the switch. One distinction I should make, though, is that I drive a stick, not an auto.

(EDIT: I thought I should say that I've made no modifications to the engine or exhaust [no CAI, flashpaq, et al], in case that figures into your equation.)

mountainneer 06-14-2013 11:46 PM

I have a 2010 JKU auto with 35's. I went with 5.13's. I think it's perfect with 35's, might be a little much if your keeping 33's.

brendan614 06-15-2013 09:07 AM

Quote:

Originally Posted by rics1997 (Post 3862366)
I am running 4.88 with 35 MTR's. I started with 3.73's myself. I know many on here pushed 5.13 when I was getting mine but the shop I used said you really should get the 4.88 unless going to 37's in the future and I am glad I took their advise. I was running 33 Duratrac (32.5) and I really wasn't a fan when on the highway. The rpm's were pretty high at 75mph on the highway and at that speed I was getting less gas mileage then in the City. I moved up to 35's and happy with the combo. I get great get up and go and better highway rpm at around 2500rpm's at 75. I think those that push 5.13's are JKU's. The heavier 4dr might need the extra push but with my 2dr I like the 4.88's better

That's my opinion though from the way mine runs

Thanks rics1997 for your opinion man!

What I'm trying to wrap my head around is the tire size. On the Nitto spec sheet my tires are 33.54", but in reality they're much smaller once they're mounted, you set the p.s.i. and do the chalk test. I even had to play with my SC Flashpaq several times to get the speedo right. I think I have it set at 31.75" and the speedo is dead nuts. So in selecting a gear ratio, do I go by the manufacturers specs or the actual running size of the tire?

brendan614 06-15-2013 09:24 AM

Quote:

Originally Posted by JKralph (Post 3862398)
I have a very similar experience to rics.

I drive a 2dr 2010, and I regeared not too long ago to 4.88. I'm currently running 33" duratracs, and at 70 mph I'm turning just about 3000 rpm, which is a bit high IMO, but I plan on 35s in the future, so I'm not too worried about it (particularly now that I've read rics post :D).

I would not have gone deeper than 4.88, and I had considered 4.56 for a while, and I'm sure either is fine. 4.56 would have been my choice if I wanted to stick with 33's.

I've only had one chance to wheel it since regearing, but it was night and day. Then again, I was moving from 3.21's to 4.88's, so that could have something to do with it.

Overall, very happy with the switch. One distinction I should make, though, is that I drive a stick, not an auto.

(EDIT: I thought I should say that I've made no modifications to the engine or exhaust [no CAI, flashpaq, et al], in case that figures into your equation.)

Thanks JKralph! I'll probably never go larger than what I have now. This is my daily driver and I commute about 100 miles a day. The largest I'll ever go is 285/75R17 (34"). Reason being is I like my Moabs too much and I've already invested in the Spidertrax wheel spacers.

brendan614 06-15-2013 09:27 AM

Quote:

Originally Posted by mountainneer (Post 3862466)
I have a 2010 JKU auto with 35's. I went with 5.13's. I think it's perfect with 35's, might be a little much if your keeping 33's.

Thanks bro! What RPM are you running at highway speed? I'm trying to find a balance of performance and economy. Maybe that's an oxymoron lol!

Gily 06-23-2013 07:29 PM

Will I be om running 37"s with 5.13?

brendan614 06-23-2013 10:07 PM

Quote:

Originally Posted by Gily (Post 3891969)
Will I be om running 37"s with 5.13?

Do you have an auto or manual?

Gily 06-23-2013 10:39 PM

Quote:

Originally Posted by brendan614 (Post 3892536)

Do you have an auto or manual?

Auto, 2011 3.8L...


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