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Old 11-23-2011, 05:35 PM   #1
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get some power back in my TJ?

I have a 1998 4.0L Jeep Wrangler Sport that is getting up there in the miles (~205,000). It runs great but it is starting to show its age... I have already bored out the manifold, put a K&N intake system on it and a Borla cat-back exhaust on it and I'm only running a 2in lift and 31's because it is still my daily driver for the time being. Does anyone have some recommendations on how I get a little more power out of the inline 6? (aside from a super charger or a turbo charger, letís be realistic haha)

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Old 11-23-2011, 05:43 PM   #2
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Take a look at the ratio tag at the 9 o'clock position on your front or rear differential cover and tell us if it says 3.07 or 3.73? If it says 3.07, regearing to a lower ratio like 3.73 to boost your engine rpms will make a significant boost in performance. Your K&N air filter did nothing for performance, though it did significantly help increase how much dirt is getting into your engine now. K&N air filters are horrific at how much fine dirt they pass.

The tag in the below photo is indicating a 3.73 ratio, inside the red circle.
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Old 11-23-2011, 06:54 PM   #3
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Replaced the CAT on my 97 4.0. Made a big noticable difference in get-up and go.
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Old 11-23-2011, 07:24 PM   #4
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3:73 or 4:11 gears will be your best option
or smaller tires
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Old 11-23-2011, 07:32 PM   #5
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Gears will really wake up a car! Keep in mind that you will run at higher rpms on the highway.
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Old 11-24-2011, 12:21 PM   #6
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O2 Sensors... Had the one closest to the engine replaced and my 1997 TJ acted like it just rolled off the lot. There also was a problem long ago with the wires going to the connector on that sensor scraping bare.
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Old 11-24-2011, 12:25 PM   #7
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Keep in mind that you will run at higher rpms on the highway.
Which is a good thing when your rpms are too low due to improper gearing for the size tires being used.
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Old 11-24-2011, 01:38 PM   #8
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Exactly! And since I live in Pittsbugh, PA where a level road is anything under a 30 degree incline, drive a 2.5L 4 Cyl with 31x10.5 BFG AT/KO's.... even with the 4.11 gearing, I really need all the uumph I can get. No complaints. The TJ has plenty of power but when I got this unexpected boost, I loved it!!

obtw, Jerry's right, the 4.11 gearing is awesome!
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Old 11-24-2011, 04:40 PM   #9
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Looks like I've got the 3.07's, So it sounds like my best bet is changing the gear ratio. This might be kind of a dumb question but, sometime in the near future I am planning on putting lockers on it, so does that kind of negate changing the gear ratio now?

FYI: my plan is to get a new daily driver at some point and turning this Jeep into a more serious off roader. Kind of debating the steps to take at this point...
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Old 11-24-2011, 04:59 PM   #10
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Quote:
Originally Posted by msigler View Post
Looks like I've got the 3.07's, So it sounds like my best bet is changing the gear ratio. This might be kind of a dumb question but, sometime in the near future I am planning on putting lockers on it, so does that kind of negate changing the gear ratio now?

FYI: my plan is to get a new daily driver at some point and turning this Jeep into a more serious off roader. Kind of debating the steps to take at this point...
It would definitely be more cost effective labor wise if you did the lockers and gearing at the same time. But here's the thing, are you going to go with 33s or even 35s at some point? If so and you replace with 3.73 now you will need to re-gear again later.

By the way...it's best to buy the lockers and gears through the shop that is going to install them.
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Old 11-24-2011, 05:00 PM   #11
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Quote:
Originally Posted by msigler View Post
Looks like I've got the 3.07's, So it sounds like my best bet is changing the gear ratio. This might be kind of a dumb question but, sometime in the near future I am planning on putting lockers on it, so does that kind of negate changing the gear ratio now?

FYI: my plan is to get a new daily driver at some point and turning this Jeep into a more serious off roader. Kind of debating the steps to take at this point...

It's best to do the lockers and gears at the same time to save a bit of time and money on labor. Also I would regear to the tire size you want to go to instead of what you have. If you put in something like 4.11s, then step up to 33" tires in a month, then you will be undergeared slightly.
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Old 11-24-2011, 05:18 PM   #12
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It would definitely be more cost effective labor wise ...
Quote:
Originally Posted by InvertChaos View Post
It's best to do the lockers and gears at the same time ....

Beat ya!

But then again you have the power to change time so I better shut up.
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Old 11-24-2011, 05:20 PM   #13
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I think gears would be an awful investment when hes already got 200k on the jeep. Try a nice tune up with new wires, plugs (like the autolite platinums jerry reccomends all the time), coil, and distributor cap. Also a good gunk cleaning throughout the intake manifold always helps. If you really want a part could try a 63mm straight through TB off ebay to give it a little more pep in combo with your CAI. Your best bet is to try to fight up the things that are causing your motor to start bogging down from age like gunk or old parts.
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Old 11-24-2011, 05:48 PM   #14
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Quote:
Originally Posted by gus54

Beat ya!

But then again you have the power to change time so I better shut up.
Heh heh
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Old 11-25-2011, 12:57 AM   #15
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Whats kickin everyone. Deer Slayer here. I'm new to the forum. Hope everyone had a wonderful turkey day. One of the things I've been considering is a header and new exhaust. I can do that but, not to sure about my abilities with the gears. Tryin to boost the horse power instead of getting into the axles. I am also running 31x10.50x15's with a 2.5" lift on a 2006 Wrangler with a 4.0. It also has an auto trans. Anyone tried that?

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