[famousperson]

I am a newbie on this forum, and although I have owned my stock '03 Rubicon since 2007, I am a total virgin when it comes to messing with it.

I do mostly city driving and find the 4.0 to be sluggish and a gas hog (10 mpg). I would like to move up a step to a V6 or small V8. I've gone online and read about various engine swaps but would like the opinion of the people here.

i would like to keep the same transmission (manual, 5 speed), xfer case and drive shaft, but maybe do away with the 4.10 rear end. i would prefer a swap where a kit exists for all necessary adapters (engine mounts and so forth). i don''t care about off road ability as that's not something I do.

i would appreciate any suggestions regarding suitable engines, drive trains and kits, online sources or any other information would be appreciated.

Thanks.

Peter

 

[Serious Offroad]

5.3L Vortec is very popular swap. (I've got one in my XJ.)
The engines are incredible and there is plenty of aftermarket support.

 

[Chris]

5.2's are also getting more common. I did a 5.9 swap in my YJ.

 

[aw12345]

Is it on stock tires still? the 4.0 in stock form should have ok power with stock tires and stock gearing. Also it should get considerably better milage than 10 mpg in stock form

 

[Ggg]

He says its a Rubi so one size bigger tire and 4.10 gears IIRC. I agree sounds like something else is wrong. Even the 4 cyl with its stock tires is ok for power.

 

[aw12345]

He says its a Rubi so one size bigger tire and 4.10 gears IIRC. I agree sounds like something else is wrong. Even the 4 cyl with its stock tires is ok for power.

I am well aware that a stock Rubi has 31" tires.
That doesn't mean this one is bone stock, is why I asked big tires and 4.10 gears would kind of explain what is going on

 

[Chris]

It definitely sounds like something else is wrong. I never had any power issues with 4.2 or my 4.0 and I was on 3.07 and 3.55 gears and 33's. I got mid teens in my 4.0 but in my 4.2 I was lucky to get 10 mpg but that was carbed and if I got it tuned for mileage it sucked everywhere else.

 

[Cstevens]

I have been told that a step up to 4:56 gears yields a noticeable improvement in power....not sure about the gas mileage though.

 

[famousperson]

Thanks for all the suggestions re engine swaps and my poor performance. Sorry i didn't mention that my Rubicon is bone stock, with the exception of having more aggressive tires mounted. Could the dual purpose tires be doing me in?

 

[Chris]

Should not be if they are the same size as stock.

 

[Ggg]

I am well aware that a stock Rubi has 31" tires.
That doesn't mean this one is bone stock, is why I asked big tires and 4.10 gears would kind of explain what is going on

I wasn't directing my comment at you, just commenting out loud. But the word "stock" in the middle of the first sentence should have been a clue it's a stock Rubi.

 

[Ggg]

Thanks for all the suggestions re engine swaps and my poor performance. Sorry i didn't mention that my Rubicon is bone stock, with the exception of having more aggressive tires mounted. Could the dual purpose tires be doing me in?

No need to apologize you made it perfectly clear it was a stock Rubi in the first sentence, sometimes people read too fast and don't comprehend what they just saw. I've made the same mistake myself.

 

[Steelman]

Did this get resolved? Curious...

 

[Kelowna]

It should do a lot better than 10 MPG , that makes me think something is wrong with it.

 

[Steelman]

Mine gets 10-ish MPG, but it's got 33's, 4:10 gears and an auto trans...that Rubi should def do better than that!

 

[famousperson]

Me, too. But it starts and runs just fine. I changed the plugs (which, upon examining the old ones wasn't needed) and that made no difference. I've looked at changing the gear ration--I assume it's 4.10--but the cost of the swap pays for a lot of gas. How much difference do tires make? I've got some pretty aggressive Wranglers on, now, but would switch them out in a heartbeat if I thought it would matter.

Peter (OP)

 

[mrclean]

A rubi is set up for off road driving. I have heard the mpg isn't so great with them but consider it was built for off road. I agree with others - seems something is not right but I don't think you are going to get the mileage you are looking for without turning it into something it wasn't meant for. I would suggest trade or sell and get into a more setup for street wrangler. Stupid question but are the axle lockers on?

 

[Kelowna]

My son drives an 04 Rubi, with 3 inch lift, and 34's for tires, in Yokohama Mud style. He says in mixed driving city/ highway he gets 17 mpg tank after tank. He is his fathers son, meaning not driving like and old granny, he isn't afraid to put his foot in it. Sometimes a driver makes the largest difference in MPG, I did a long road trip with my daughter 2 summers ago, she got substantially more miles per tank than me, when she was driving. Because she drives a lot slower, and doesn't spin my cars engine hard as she goes up through the gears. She would usually shift in the 3,000 RPM range, its a rare day if I shift it under 5,000. She drove the speed limit or just over most of the time, and on the open roads, light traffic, I drove 40 to 80 over as much as I could.

 

[Steelman]

My son drives an 04 Rubi, with 3 inch lift, and 34's for tires, in Yokohama Mud style. He says in mixed driving city/ highway he gets 17 mpg tank after tank. He is his fathers son, meaning not driving like and old granny, he isn't afraid to put his foot in it. Sometimes a driver makes the largest difference in MPG, I did a long road trip with my daughter 2 summers ago, she got substantially more miles per tank than me, when she was driving. Because she drives a lot slower, and doesn't spin my cars engine hard as she goes up through the gears. She would usually shift in the 3,000 RPM range, its a rare day if I shift it under 5,000. She drove the speed limit or just over most of the time, and on the open roads, light traffic, I drove 40 to 80 over as much as I could.

40 to 80 over the speed limit?!

 

[Kelowna]

Don't forget that we use kms up here, and were in my car, not Jeep. That's slow in the car.