Robs original post was more valid than yours. He actually has the 3.8. Read the op and then you'd realize your input isn't needed. I have 5.13s scheduled to be installed on my 09 jku auto in 2 weeks. Running 35 bfg mud terrains. I'll report back after install.

I'm running an 07 with auto. My gears are 4.10, and running 35". If you plan to run your 33" and never make it to the 35". I wouldn't bother with regearing. But if your going to go to 35" I would recommend changing the gears. Me personally, I'm going to leave my gears alone until a few years down the road. Just like what I would do if I was running your setup. If you go to 35" I would put 5.13 in.

And it continues

Those with manuals or the 3.6 should just keep quite unless they have experience with the 3.8 & auto. Your info is useless.

4.88 are minimum with 35s but 5.13s would be a better option for the OP.

I ran 4.10s with 32s, 33s & 35s

I ran 5.13s with 35s & now 37s

Don't fear the gear. And I have a 3.8 auto

Yep sorry missed that. Well not so much as missed it but u forgot after reading everyone talking about their pentastar gearing

I'm not sure their info is useless. Experience, probably.

That gear ratio chart I posted for the 3.8 seems to accurately reflect your experiences. I'm all about numbers. Engine rpms at 70 mph seems like a good measurement for a dialy driver. I was totally shocked to see how low the suggested gears were for the 3.8. Probably reflective of the motors lower hp and torque ratings.

Night and day difference. It doesn't hunt for gears when going uphill like it used to and it tows much better. Hope this helps.

I have 3.73s with 35s and a 3.8 under the hood and it's not horrible. I would prefer 4:10s though. Probably coming soon

I did the test at 65mph with the Over Drive in the off position and my rpm were at 2600 (with my current 2010 jku sport automatic 3.8 liters with 3.73 and 33" tires).

A local jeep dealership suggests 4:10s with 37s. Isn't that not nearly enough, especially if you have an automatic. Also it's 2k for the gears and 1k for install...ouch! Dealerships are such ripoffs!!

I got quote at 1500$ (Canadian) for 4.56 front and rear including parts and install.

Honestly I think you would regret 4.56 if you are planning on going to 35's. I would go minimum 4.88's, but that's just my opinion.

Oups, my mistake... When I said 4.56, it was if I would stay with 33". But if I go with 35" then it would be 4.88 or 5.13 I guess (same price as 4.56)

I went with Planman's advice and went with 5.38s on my 2010, auto, 4 door, 3.8L, Rubicon, 35" Nitto Trail Grapplers. IIRC there was a company making 5.38s for the D30, don't know if they still are, but the pinion gets pretty small. 70MPH has me at 2600 RPM.

4:10 was bearable around town with OD off, forget using OD on the freeway unless you have tailwind, you're going downhill or going like 10MPH below the speed limit. Only thing I felt like I gained with 5.38s was to be able to use overdrive on the freeway, I still turn it off around town since it's still a dog and shifts too much. Off road in 4L the 5.38s are spot on, basically crawls without having to touch the gas.

Gonna step up to 37s soon and most likely going to GY MTRs for their weight, about 5lbs lighter per tire than my 35" TGs. 35" MTRs are about 15lbs lighter than 35" TGs.

Are they still holding up well? Most people out here with D30's eventually break those gears.

Mentioned the 5.38s for D30s because I thought the OP had a D30. I'm running D44s.

D30 front and D44 rear

08 auto and 3:73 gears have been running 33s for 70,000 KM...90% of the time running down the QEW and 401 ect.

The old 42RLE does hunt at times, I need to kick it down on some hills...ok. my RPMs line up pretty darn close to the chart.

Am I saving for gears with these 33s?

Am I frustrated with the way my Jeep drives?

Do I feel I need more power?

Nope, no to all the above.

Am I saving for gears and 35s?

Yup.

But, I would mount the 35s first before I gear see how things are. But, have the cash ready for gears right away if needed.

From what I read, and the OP has some good advice here (Joe_B and RobsJeep...thanks Gents)

I'd do 4:88 based on what size (actual) tire I have planned, my drive, and mild off road I'm able to do.

Good luck to the OP

Thanks to all of you who took time to help me with my question about "witch" gear to go for with 33" or 35" tires.

I still have another question indirectly connect to gearing:

They say that when you put 35" tires (more weight and bigger size), you put a lot more stress on different parts (ball joints...) of the jeep and can cause some premature beak down. Now I understand this applies when you do offroad but is it the same when you do only country roads and no rocks? I'm still not sure if I will go to 35" (from 33") because of that premature wear... If this concern only jeeps doing a lot of offroad and rocks then I would feel better about choosing 35".

Ok, I lied, I have another question:

By putting on 35" (from 33") I will loose MPG (now I'm at about 12.5mpg with my stock and 33") but by also adding a flashpaq, would I get back to lost MPG? If yes or no, by switching my 3.73 gears to 4.88 or 5.13, would I get the MPG back to stock?

Thanks again for you answers