Lifted KJ fuel mileage - JeepForum.com

 
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post #1 of 5 Old 06-16-2017, 05:14 PM Thread Starter
skippy102595
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1993 YJ Wrangler 
 
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Lifted KJ fuel mileage

Just wondering what kind of MPG I should be getting running 245/70/R17's? Jeep has a 2.5" lift and looking back i didn't realize I mounted the largest size tire I could fit on a 2.5" lift until afterwards. I didn't realize that a 245/70/R16 is 1" shorter than a 245/70/R17. That being said, the tires aren't overly aggressive they are trail guide A/P's but i'm currently averaging 14mpg and that's mostly because the mpg is terrible when driving around town. It does fine on the highway as far as MPG goes. Also seems like it lacks a bit of power at the top end of each gear. Would regearing be helpful and if so what should i go with? It's a 06' 3.7L.

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post #2 of 5 Old 06-17-2017, 10:05 AM
tommudd
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2004 KJ Liberty 
 
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Location: Central OH/ Kilimanjaro,Tanzania
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Quote:
Originally Posted by skippy102595 View Post
Just wondering what kind of MPG I should be getting running 245/70/R17's? Jeep has a 2.5" lift and looking back i didn't realize I mounted the largest size tire I could fit on a 2.5" lift until afterwards. I didn't realize that a 245/70/R16 is 1" shorter than a 245/70/R17. That being said, the tires aren't overly aggressive they are trail guide A/P's but i'm currently averaging 14mpg and that's mostly because the mpg is terrible when driving around town. It does fine on the highway as far as MPG goes. Also seems like it lacks a bit of power at the top end of each gear. Would regearing be helpful and if so what should i go with? It's a 06' 3.7L.
My 04 with 265-75-16s / over 4 inches of lift / 4.10 gears and lots of weight got 21-22 on the highway easily at 75 plus MPH
My 03 with 265-70-16s and 2.5 inches of lift plus 4.10s gets about 20.5 to 21 on the highway again at 73-75 MPH

Gearing is key for a tire that large , well anything much over a 30 inch, the 3.7s have a fairly narrow power band, drop a bit below with larger tires and stock gearing and the mileage is going to take a dump, transmission runs hotter etc

So now you have effectively lowered the gearing from 3.73 to about 3.50 and to gain back to stock type gear ratios need to go to a 3.93 ( which 4.10s would work great )

MUDD'S MOTORSPORTS
04 KJ JBA 4 IN COILOVER, 32s 4.10s
03 KJ JBA 2.5 T.C. LIFT, 31s 4.10s
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post #3 of 5 Old 06-17-2017, 10:20 AM Thread Starter
skippy102595
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1993 YJ Wrangler 
 
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Location: Saint Louis
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Quote:
Originally Posted by tommudd View Post
My 04 with 265-75-16s / over 4 inches of lift / 4.10 gears and lots of weight got 21-22 on the highway easily at 75 plus MPH
My 03 with 265-70-16s and 2.5 inches of lift plus 4.10s gets about 20.5 to 21 on the highway again at 73-75 MPH

Gearing is key for a tire that large , well anything much over a 30 inch, the 3.7s have a fairly narrow power band, drop a bit below with larger tires and stock gearing and the mileage is going to take a dump, transmission runs hotter etc

So now you have effectively lowered the gearing from 3.73 to about 3.50 and to gain back to stock type gear ratios need to go to a 3.93 ( which 4.10s would work great )
Thanks Tom. Like I said, highways not a problem it's the low gears stop and go at lights where i'm pretty certain a hummer h1 would be more fuel efficient lol hopefully 4.10s would help that as well
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post #4 of 5 Old 06-17-2017, 10:56 AM Thread Starter
skippy102595
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Also what kinda donor vehicles could i be looking for? Would a CRD have the parts I need?
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post #5 of 5 Old 06-19-2017, 03:38 PM
tommudd
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Location: Central OH/ Kilimanjaro,Tanzania
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Quote:
Originally Posted by skippy102595 View Post
Also what kinda donor vehicles could i be looking for? Would a CRD have the parts I need?
Only the 4 cylinders

MUDD'S MOTORSPORTS
04 KJ JBA 4 IN COILOVER, 32s 4.10s
03 KJ JBA 2.5 T.C. LIFT, 31s 4.10s
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