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Old 05-02-2013, 10:15 AM   #1
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Question Best engine upgrade help?

I am new to Jeeps and trying to learn as much as I can. I recently purchased a 2001 Sahara and having gone from riding a Harley for fun to a Jeep (a different kind of fun) I miss the ability to maintain a decent highway speed. It seems this 4.0 has a very difficult time maintaining highway speeds without having to shift down to gain power. Is there something I can do like add a supercharger, a turbo or install a larger engine without getting into too much of a hassle? Any help would be greatly appreciated.

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Old 05-02-2013, 10:18 AM   #2
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Do you have larger than stock tires? What is your gear ratio?

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Old 05-02-2013, 10:22 AM   #3
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35" tires and 3.73 I believe, still learning about this Jeep, everything was already done to it when I bought it. Has lift kit, 35" tires, and a bunch of other stuff. Its a manual transmission. Lots of low end power but trying to drive down the highway in 5th gear (especially against the wind) drives me crazy. Seems I have to hold the pedal all the way down to the floor and/or downshift.
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Old 05-02-2013, 10:23 AM   #4
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Start by doing a google search. If you had a Harley then you know that there is an endless amount of $$ that can be spent. Jeeps are no different and probably even worse depending on how far you want to go....gears, axles, tires, V8 conversions, etc.
Give us some info on the current specs of your TJ and that will give a starting point...tire size, gear ratio, trans type, what your intended uses are going to be ect.

If you want to drop some fairly serious $$ on a motor conversion for instance,then as a suggestion, read thru my build thats in my signature. I absolutely have no issues maintaining any speed I want..but it aint cheap...
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Old 05-02-2013, 10:25 AM   #5
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35" tires and 3.73 ...35" tires...manual transmission.
regear to 4.88s & install the correct speedo gear. problem solved.
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Old 05-02-2013, 10:26 AM   #6
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Your issue is that 3.73 gear ratio. Re gear to 4.88 and it won't be an issue.
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Old 05-02-2013, 10:27 AM   #7
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Originally Posted by ssgmiller558 View Post
35" tires and 3.73 I believe, still learning about this Jeep, everything was already done to it when I bought it. Has lift kit, 35" tires, and a bunch of other stuff. Its a manual transmission. Lots of low end power but trying to drive down the highway in 5th gear (especially against the wind) drives me crazy. Seems I have to hold the pedal all the way down to the floor and/or downshift.
The 35" tire/3.73 axle ratio combination is the sole reason for your lack of power. There is nothing you can do to the engine to fix the type of loss of power that combination causes.

The way to restore the engine power & allow you to maintain speed even on steep grades is to regear your axles which will bring the RPMs back up to where they were when the Jeep left the factory. That is done by replacing the ring & pinion gears in both of your axles with a lower ratio replacements which will bring the engine RPMs back up to where they should be. The larger tires have reduced the engine RPMs at highway speeds so much that the engine can't develop as much power.

If your transmission is the 5-speed, 4.88 is the optimal ratio for a 35" tire. Once I regeared my previous TJ to 4.88 for its 35" tires, it was a pleasure to drive again. The cost of regearing both axles (both must be done) including all parts & labor is typically $1300-1500 depending on the shop.
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Old 05-02-2013, 10:30 AM   #8
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Your best bet is a regear. Go to 4.56's... Or 4.88's if you plan on going bigger than 35 inch tires. You can buy chips and cold air intakes all you want... But the fact of the matter is you're trying to drive an underpowered brick at 70mph against the wind. If i were you... I'd get a regear and get some lockers put in while you're at it. You'll save money as they'll have everything taken apart regardless. No sense paying for the same work twice.

I have an 06 TJ with 35's and 4.10's. 6th gear is okay on the highway... But it's not as deep as your NV3550 in top gear.
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Old 05-02-2013, 10:30 AM   #9
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Quote:
Originally Posted by sduncan View Post
start by doing a google search. If you had a harley then you know that there is an endless amount of $$ that can be spent. Jeeps are no different and probably even worse depending on how far you want to go....gears, axles, tires, v8 conversions, etc.
Give us some info on the current specs of your tj and that will give a starting point...tire size, gear ratio, trans type, what your intended uses are going to be ect.

If you want to drop some fairly serious $$ on a motor conversion for instance,then as a suggestion, read thru my build thats in my signature. I absolutely have no issues maintaining any speed i want..but it aint cheap...:d
wow that's awesome!!!
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Old 05-02-2013, 10:34 AM   #10
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Thanks for all the reply’s! Sounds like the first thing I’m going to do is figure out how to do the 4.88 gearing for those 35" tires
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Old 05-02-2013, 10:34 AM   #11
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Your best bet is a regear. Go to 4.56's... Or 4.88's if you plan on going bigger than 35 inch tires. You can buy chips and cold air intakes all you want... But the fact of the matter is you're trying to drive an underpowered brick at 70mph against the wind. If i were you... I'd get a regear and get some lockers put in while you're at it. You'll save money as they'll have everything taken apart regardless. No sense paying for the same work twice.

I have an 06 TJ with 35's and 4.10's. 6th gear is okay on the highway... But it's not as deep as your NV3550 in top gear.
4.56 would be fine with the 6-speed transmission you have and 35" tires but the OP has a 5-speed where 4.88 is the optimal ratio for 35" tires. 4.56 isn't quite enough gear for 35" tires & the 5-speed combination.
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Old 05-02-2013, 10:35 AM   #12
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Thanks for all the reply’s! Sounds like the first thing I’m going to do is figure out how to do the 4.88 gearing for those 35" tires
simple: take it to a drivetrain shop and have them install 4.88s gears. should cost between $1200-1800 depending on your area & the parts used.
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Old 05-02-2013, 12:47 PM   #13
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regear to 4.88s & install the correct speedo gear. problem solved.
X2 on regear
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Old 05-02-2013, 01:25 PM   #14
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Yes regear. I followed their advise and am stoked about the results. Plenty of power to run down the road at 70+ if I choose and even better on the trails.

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Old 07-15-2013, 08:06 PM   #15
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I'm new to this site and been trying to figure out what would be better to add new my 2013 JK sport. A turbo? Or a supercharger? I've researched RIPP for superchargers and STS and PRODIGY PERFORMANCE for turbos

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