I have a 2004 Wrangler Rubicon with Dana 44s, 4" suspension lift, 2" body lift with 35" tires. It has manual transmission and I get about 8mph in town. When I take it out on the highway, my 5th gear is pretty much useless until I am going 65-70mph and on a flat stretch of roadway. I'm wondering if I should change out my gears to get better response in my upper gears? Besides dropping a new motor in, is there anything I can do to increase my gas mileage? Are these two problems (gears and gas mileage) related or two separate issues?
Improving Gas Mileage
- Thread starter mstrait21
- Start date
Is your speedometer corrected for 35's this could add about 15% to your mileage. Regearing will help a bunch
Regear it to 5.13. Then you'll get 13-14 MPG highway. 
p.s. I hear you can get 42 MPG with a Fram oil filter. @bohuggabee told me so.
https://wranglertjforum.com/threads/oil-considerations-10w40-vs-10w30.85051/
p.s. I hear you can get 42 MPG with a Fram oil filter. @bohuggabee told me so.
https://wranglertjforum.com/threads/oil-considerations-10w40-vs-10w30.85051/
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Math is hard.How much would that improve his 8 MPG?
less than 2 but many people don't think about that
Math is hard.
9.2 ish...
I hate to give away my better MPG secrets, but.......
Mudflat
TJ Enthusiast
If you don’t have the correct speedometer drive gear (see the attached chart) then you don’t really know what your mpg is. From your description & assuming you still have the stock Rubicam 4.10 gears it seems obvious that you are undergeared. I would say that you would want 4.88 gears to be happy on the road, but many here would say you need 5.13s.
I had a similar problem when I first bought my Wrangler “X”. The previous owner put on a lift & 33” tires, but kept those terrible 3.08 gears. Changing to 4.56 made it a whole ‘nother Jeep. MPG should improve because you won’t have your foot to the floor all the time.
Good luck & let us know how this works out for you.
I had a similar problem when I first bought my Wrangler “X”. The previous owner put on a lift & 33” tires, but kept those terrible 3.08 gears. Changing to 4.56 made it a whole ‘nother Jeep. MPG should improve because you won’t have your foot to the floor all the time.
Good luck & let us know how this works out for you.
Gearing is #1.
But look at live ODB data and your fuel trims. They should be low single digits. Higher numbers and you're running rich and dumping fuel. You can also pull and read your spark plugs.
I've had issues with low fuel pressure that dropped my mpg. I've also had a cracked exhaust header that dropped my mpg.
-Mac
But look at live ODB data and your fuel trims. They should be low single digits. Higher numbers and you're running rich and dumping fuel. You can also pull and read your spark plugs.
I've had issues with low fuel pressure that dropped my mpg. I've also had a cracked exhaust header that dropped my mpg.
-Mac
The OP should be able to acheive 13-16 mpg.
Rubicon 241OR transfer cases don't use a speedo gear. A speedhealer or similar electronic signal modifier is the only option.
Aligning the gear ratio to the tire size is going to help alot in terms of efficiency. The foundation stems from putting the 5 ratios in more useful ranges for your style of driving. The three ratios available are 4.88, 5.13 and 5.38.
You can figure out pretty accurately where you'll be at certain speeds in each gear with the grimm jeeper gear calculator and your real tire size (34.n"). Generally each step in ratio will step rpm up by 200 at highway speeds.
Beyond this, having everything in good running condition helps. No vacuum or exhaust leaks. No calipers dragging. You can pick up a little power with intake, exhaust, shorty headers, 1.7 roller rockers and tune. This means less time on wide open throttle. Electric fan could get you a little more. Using a more efficient tire, possibly at a bit higher psi, maybe +1 mpg there.
Rubicon 241OR transfer cases don't use a speedo gear. A speedhealer or similar electronic signal modifier is the only option.
Aligning the gear ratio to the tire size is going to help alot in terms of efficiency. The foundation stems from putting the 5 ratios in more useful ranges for your style of driving. The three ratios available are 4.88, 5.13 and 5.38.
You can figure out pretty accurately where you'll be at certain speeds in each gear with the grimm jeeper gear calculator and your real tire size (34.n"). Generally each step in ratio will step rpm up by 200 at highway speeds.
Beyond this, having everything in good running condition helps. No vacuum or exhaust leaks. No calipers dragging. You can pick up a little power with intake, exhaust, shorty headers, 1.7 roller rockers and tune. This means less time on wide open throttle. Electric fan could get you a little more. Using a more efficient tire, possibly at a bit higher psi, maybe +1 mpg there.
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