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Old 08-19-2015, 01:13 AM
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3.8 Auto Gearing Confusion

Okay, so like the title says.....I have a 3.8L Automatic Unlimited Rubicon, from what I know all 07-11 Rubicons had 4.10's standard till 2012 where it was an option (at least...I think...)

I honestly don't know lol. I've seen conflicting info on this topic in many places so it's time to ask.

Tomorrow (or later this week) I will be taking my Jeep to the dealer to get some questions answered on it (such as what gear ratio I do have to confirm if I have 4.10's) among other things. But for now, I've been back at research on tire sizes and gear ratios that match to the 3.8 and 4 speed auto.

Yes I have seen the gear ratio chart for the 07-11's, so according to it for my 2010 with the auto, rubicon having 32" tires, at 70 mph I'd be at 2017RPMs (give or take) and in the "Minimum Allowable Gear Set, sluggish, minimum OD use, mild trail use at low elevation" so it "works" but is not ideal for highway driving. Seeing as how it is a basically stock Jeep (no performance altering mods) and a 2010 with 82000 miles on it can't have been all that bad.

That said, I know that for sure I would rear gear but it would be a short while to build up the cash for it. Other forums have said for a short solution to get the Procal (which was an obvious purchase either way and I assume this is the right thing? American Expedition Vehicles - Brute Kit, V8 HEMI, Aftermarket Jeep Conversions, Products, Wheels, Accessories and Highline Kits for Jeeps (TJ, JK, WK, XK). )

When I do go to a larger size tire it will be between 33's to 35's (undecided still, got plenty of time to decide either way) but for the most part I really just want a lot of this mess cleared up. Sorry for the length or if it's hard to read, tried to fit in all the details I could.

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Old 08-19-2015, 01:44 AM   #2
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If you go to the General Jeep Discussion area up top you'll see the "stickies" threads, tap on there and scroll down to the vin decoder thread. It'll take you to a link where you put in your vin# and it will show you all the options that are on your jeep including gear ratio. I have an 07 Sahara auto with 285-70-17 tires and 4.10 gear ratio. Granted it's a 2dr and lighter than the 4drs it drives just fine for the 90% time on the street and 10% time on the trails for me. Yes it could use more power and a regear but until I can save up it works. You might want to check out Superchips Flashcal also, same price as the aev programmer but can be updated later to the Flashpaq.

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Old 08-19-2015, 10:49 AM
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See I saw that too and was going to look into it when I had time. I had a Flashpaq for my Durango to make it run a 91 octane tune for more power (that with intake, exhaust, 180 degree thermostat and it felt so much more powerful, was awesome) so I know the magic that Superchipz can do.

So you have a 2 door with a 3.8, Automatic, 33's (technically) and 4.10s and it's just fine? Just that even works for me. It's a Jeep so I'm not expecting it to have near as much balls as my Durango did but even so I wanna do it right.
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Old 08-19-2015, 11:30 AM   #4
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One of our JK's is a 07 2Dr, Auto, 4:10's and we run 35's on it. At one point we ran the FlashPaq on it and it helped a lot. Now we just run the FlashCal on it (like a ProCal but cheaper) and it works good to. I say lets look at a tuner/programmer now. Then when you do the larger tires, think about regearing. It is not as bad as you would think unless you live in Colorado or somewhere like that. Never been to MO but guessing it is pretty flat...

Superchips FlashCal Programmer, JK 2007-15

Let us know if we can help.

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Old 08-19-2015, 12:46 PM
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Mo is actually littered with small hills thanks to the Ozark Mountains. There's flat spots around but Kansas is nearly all flat lol.

I'll give the FlashCal a look.
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Old 08-19-2015, 01:22 PM   #6
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Your 2010 Rubicon definitely came with 4.10's from the factory. In 2010 all autos and manuals had 4.10's standard. It changed in 2012 for auto Rubicons.
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Old 08-19-2015, 02:13 PM
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Cool so I'm right, 07-11 4.10s standard and 12+ was an option.
Thanks Kik.

Also, after some looking on Vin Decoder, it's apparently a 2008. Doesn't make sense to me since I was sure it was new when my dad bought it back in 2010, it had only 12 miles on it (my Durango had 8 off the lot from being test driven around some)
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Old 08-19-2015, 04:17 PM   #8
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Quote:
Originally Posted by MoparLeprechaun View Post
Cool so I'm right, 07-11 4.10s standard and 12+ was an option.
Thanks Kik.

Also, after some looking on Vin Decoder, it's apparently a 2008. Doesn't make sense to me since I was sure it was new when my dad bought it back in 2010, it had only 12 miles on it (my Durango had 8 off the lot from being test driven around some)
Your driver's side door/jamb will also confirm the build date, month and year, it's right there.
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Old 08-19-2015, 04:20 PM
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Yeah that sticker actually got removed somehow. Not sure when, or why, but I want it back. When I head to the dealer eventually I'll be getting a new one.
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Old 08-19-2015, 07:14 PM   #10
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Good discussion. Will the flashcal also adjust the shift points if you run 35's on 4.10 gears?
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Old 08-19-2015, 07:45 PM   #11
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Good discussion. Will the flashcal also adjust the shift points if you run 35's on 4.10 gears?
You set the "actual" tire size and that takes care of the trans. for an auto.
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Old 08-19-2015, 08:05 PM   #12
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Kik is correct that by inputting the correct tire size with the flashcal in will put the jeep back into the correct parameters for the transmission shift pattern and will recalibrate so the speedo will be correct. You can only change the factory shift pattern with a flashpaq.
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Old 08-19-2015, 09:33 PM
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You can only change the factory shift pattern with a flashpaq.
Back to what you said earlier, "You should get the Flashcal, then you can upgrade to the Flashpaq" so you mean the Flashcal can be upgraded to the Flashpaq with software? If so that'd be awesome.

I know as a Jeep I shouldn't expect to get awesome performance but I would like to get some slight better performance, mainly just because I can lol. While saving up for a lift + wheels and tires I'll be getting some things on the side as well such as an HD tire carrier, maybe front and rear bumpers, most likely exhaust, and probably dual battery setup when I upgrade the sound system and get a light bar (and possible winch but that's doubtful).
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Old 08-19-2015, 09:44 PM   #14
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Quote:
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Back to what you said earlier, "You should get the Flashcal, then you can upgrade to the Flashpaq" so you mean the Flashcal can be upgraded to the Flashpaq with software? If so that'd be awesome. I know as a Jeep I shouldn't expect to get awesome performance but I would like to get some slight better performance, mainly just because I can lol. While saving up for a lift + wheels and tires I'll be getting some things on the side as well such as an HD tire carrier, maybe front and rear bumpers, most likely exhaust, and probably dual battery setup when I upgrade the sound system and get a light bar (and possible winch but that's doubtful).
Yes the flashcal can be upgraded with software to make it a flashpaq... At an extra cost.
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Old 08-19-2015, 10:52 PM
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Good to know. Also been looking at the Traildash (and new Traildash 2 coming end of the month) and so far one of the threads I have read (which has posts dating back to about a month ago ish) says that its really just a pretty gauge pod and expensive flashcal lol.

While I'm thinking of it, would the Flashcal/Flashpaq help the computer when I do the exhaust? I know it's over the top but there's a good chance when I do jump on that that I will do a full custom system from headers to the arse? lol
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Old 08-20-2015, 12:45 AM   #16
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Neither one will help or hurt if changing the exhaust. The reason I personally recommend the Flashcal over the Flashpaq is cause the Flashpaq sets up standard parameters in its upgraded tuning to work with all the jeeps. Since no two jeeps run the same some see a little improvement and some see none. The only true way to get the most out of tuning a vehicle is to have somebody who knows what they are doing plug in a specialty tuner and adjust everything according to how your vehicle runs. Since I'm still relatively new to Jeeps I'm still looking for that person lol. I know Diablo tuners in the right persons hand can do wonders for Ford owners and Black Bear Performance For GM is amazing.
In all reality the only way your going to get any hp out of your jeep is by having motor work done (ie: changing to a performance camshaft, lifters, etc) or by adding a turbo or supercharger. Changing the muffler in all reality will only change the sound of your jeep and the headers will only move where your powerband is ex: right now let's say your powerband is between 1400rpm to 2100rpm, the headers would prob change it to 1600rpm to 2500rpm.
Sorry for such a long winded response, but I would recommend just going with the gear swap and using the Flashcal to recalibrate for the new gears and tire size then save up for the new Banks Engineering Turbo system that I hear is suppose to be pretty amazing for us 3.8 owners.
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Old 08-20-2015, 01:24 AM
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Oh I'm not after power with doing a full exhaust, that's mainly just to make something that looks so good sound just as good. If I wanted to get more power out of the Jeep I'd Hemi swap it, 6.4L (since it's a bored and stroked 5.7 with bigger cam and stronger internals) diablo sport trinity tuner, full exhaust, intake, fuel system, etc. but Jeeps aren't race cars lol.

In that case, I'll go with a flashcal, do the engine work I want to do, and if I want to get it tuned to all work together like a well greased machine then I suppose I'll get to searching, and of course I'd let everyone here know.

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