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Old 09-16-2009, 12:28 PM   #1
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Help with gearing, gas milage, what next??

So my 2003 has a 4'' lift with 33 12.50 15's, has the 6 cyl and Auto trans. i know its a jeep and gas milage sucks, but holly geeze i have little over 1/4 tank left and only 135 miles so far, im sure i could squeeze some miles out of it and run it till the fuel light comes on, but i normally fill up at 1/4 tank. My nissan titan is a V-8 with same size tires, but no lift 4x4 and i get atleast 250 out of a tank..

So why the crappy gas milage? I know its got a dana 35 axle in the rear and a 30 in the front, but no plate on the diff to tell me what gears are in there? Im pretty sure to make the milage better i need to swap gears, but to what im not sure, and what are the pro's/Cons for doing that.. Something else thats strange is when im running say 45-50 down the road, its not like the Rpms are 2500-3000 plus, i try to keep it under 2000, and normally cruise just above 1500, but every now and again it gets over 2000 when going up hill. I wouldnt think the motor was working that hard to turn the tires and maintain speed, seems to be pretty smooth, but gas milage stinks....

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Old 09-16-2009, 01:35 PM   #2
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help

Surley someones got the answer

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Old 09-16-2009, 02:06 PM   #3
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Use these formulas to guestimate your gear ratio. Calculate your actual speed first before using the "Gear Ratio" formula.
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Just bought a True Hi9 rear and a D44 front, both with ARB's and 4.88 gears!! Check out the build!
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Old 09-16-2009, 03:03 PM   #4
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gearing

had the dealer check the VIN and i have 3.73 gearing
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Old 09-16-2009, 03:17 PM   #5
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Jeep = brick.

Titan = Japanese, they somehow squeeze good mileage and impressive HP out of an engine. Then there's the Aerodynamics. its a truck, so its inherently bad...but I can without a doubt say its not as bad as a stock jeep, let alone a lifted jeep.

How big is the tank on the Titan?

IIRC Jerry B posted something around a 4.56 ratio being good for 33's. I can't quote him on that, but He'll likely be here in a few to comment. if not PM him.

I get 240-260 out of 14.4-14.7 gals stock ride height 2001 4.0L, 5spd manual, 3.73 gears. on 31x10.5x15
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Old 09-16-2009, 03:20 PM   #6
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When you fill up how many gallons are you putting in?
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Old 09-16-2009, 03:54 PM   #7
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You have a 03 TJ so you have a 19 gallon tank. At 1/4 tank I put in 11 gallons
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Just bought a True Hi9 rear and a D44 front, both with ARB's and 4.88 gears!! Check out the build!
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Old 09-16-2009, 06:28 PM   #8
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My recently lifted (2' BB) now drinks like a fish and then some. Huge difference once the oversized tires fitted, can actually watch the gauge move .... holly crap its a jeep thing
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Old 09-16-2009, 06:46 PM   #9
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Are you running the correct speedo gear?
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Old 09-16-2009, 08:01 PM   #10
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Quote:
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Are you running the correct speedo gear?
Nope not me, it's only 10km/h out at 50km/h and I use a GPS for true milage and speed
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Old 09-16-2009, 08:24 PM   #11
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Quote:
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Nope not me, it's only 10km/h out at 50km/h and I use a GPS for true milage and speed
Also, just pulled the catalytic converter to pieces. Actually cut the top off it and removed the insides, welded it back together and refitted leaving all the sensors in place. As far as I can tell it was blocked at 55000km having a 1cm looking hole at the other end as I looked through, very scientific Any who .... so far so good, milage better thus far, will wait for ECU to remap. I test only tank to tank refills with milage reading, not accurate but works for me. Also removed restrictive airfilter box horn and installed underhood snorkel, my design
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Old 09-16-2009, 08:30 PM   #12
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Also, just pulled the catalytic converter to pieces. Actually cut the top off it and removed the insides, welded it back together and refitted leaving all the sensors in place. As far as I can tell it was blocked at 55000km having a 1cm looking hole at the other end as I looked through, very scientific Any who .... so far so good, milage better thus far, will wait for ECU to remap. I test only tank to tank refills with milage reading, not accurate but works for me. Also removed restrictive airfilter box horn and installed underhood snorkel, my design
strange as it may be, I took off a poor excuse for an aftermarket "CAI" and put the OEM on, with an Amsoil drop in filter. I actually saw an improvement in my mileage.
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Old 09-16-2009, 09:44 PM   #13
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catalytic converter

I was actually curious about this, does my Jeep really need this, I would like to remove this and straight pipe it into a muffler? I dont have any sensors in it so thats not a problem, just curious if removing it would cause more problems?
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Old 09-17-2009, 12:01 AM   #14
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Also removed restrictive airfilter box horn and installed underhood snorkel, my design
I would be interested in seeing some pic's, if you could.

Thanks

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