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hello peeps. looking to buy my wife an 08 4dr rubi, automatic. just wondering what you all think of your 3.8L??? i've read all the speculation about future powerplants but we are looking to buy now. the 3.8 with the 4spd is the only thing keeping me from purchasing TODAY.
thanks!!
 

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Ok, I guess I'll be the first.........

The 3.8 is ok in stock X trim, can't say on the Rubi. Larger than stock tires of course will rob power, but nothing gears can't take care of. I haven't had much trouble out of mine other than an oil leak that won't go away. I've put a drop in K&N in and just recently put on a Flowmaster 50, seems like its breathing better now. It's a V-6, what else can you say? If you're used to a V-8 like I was, it's anemic at best, but the fun factor of offroading makes up for it.

What have you heard about other powerplants?

Good luck choosing and welcome to the board!!
 
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I'm happy with mine. I've had two other Jeeps with the in line 6 4.0L. This engine is different in that it "buzzes" higher RPM. Other than that, it seems to have adequate power (no Jeep really seems to have enough for street use) and has given me no problems yet.
 

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I'm happy with mine. I've had two other Jeeps with the in line 6 4.0L. This engine is different in that it "buzzes" higher RPM. Other than that, it seems to have adequate power (no Jeep really seems to have enough for street use) and has given me no problems yet.
x2

ditto

my thoughts exactly

seems u need at least 3 characters to reply....so there
 

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so far its done well. My Jeep was never stock so I have nothing to compare to with my larger tires. A regear takes care of most complaints. All i have is a K&N air filter and its manages to move. The key is learning how to drive the thing. I know with the auto if i put the pedal to the floor it doesnt do as well as putting it down about 3/4 of the way. Keep it in the power band and your good.
 

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My opinion

I'll admit, the engine was a bit disappointing at first (especially since I went from a V-8 Lincoln LS to a 2 door JK). But now that I've installed the Airaid CAI and TBS, I'm much more pleased with it's performance.

I'm not one to race but I've definitely been able to pass other cars, when necessary (even at a green light). Not to mention the sound is a bit intimidating to others! :thefinger:

I would assume that adding an after-market exhaust system would only improve performance and satisfaction.
 

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Since this is my first Wrangler, I honestly cannot compare it to any previous engines. I'm happy with it. I have the X unlimited 6 speed. With 35's under it, it was rather doggy. 5.13's solved that and I'm pleased again...
 

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Needs a chip to smooth out dead spots in the ethrottle. Atleast mine does. Maybe i need a CAI too...i guess ill do that mod on my day off. (docs cheap CAI)
 

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I was a bit let down at first, my last jeep had the AMC 304 that was built. So that being said after the cat back exhaust and CAI it is much better and I now have no complaints. But I am also still running 31” tires I will have to see what happens when I put on the 33 x 12.5’s. :smokin:
 

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The 3.8 has not given me any trouble. On the pavement it is a bit disappointing. In the Rubi off-roading with low gears it does not seem to make a difference. Went on a snow run last week with a group of 15 rigs - I was the ONLY stocker and was able to roll with all but the custom rock buggies. Gears, not motor, made the difference. :beer:
 

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Could anyone say how it would compare to my wife's kj 3.7? I'm 95% sure I will be getting a JK Unlimited X this summer, but it will be on pavement 90% of the time. I 'm just a little concerned about everyday drivability.
 

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Could anyone say how it would compare to my wife's kj 3.7? I'm 95% sure I will be getting a JK Unlimited X this summer, but it will be on pavement 90% of the time. I 'm just a little concerned about everyday drivability.
the girlfriend has an 07 KJ that i bought her... big diffrence. That thing is fast, compared to my JK. Of coarse I have 35" tires and I would outwheel the KJ any day. The power band is a lot diffrent though. We have a great lower power band and thats where you want it in a vehicle that is design to go anywhere. The KJ has a lot more up top. I would actually like to see some side by side dyno charts.
 

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Powers fine,.. put it (4LO & watch it Go)......:beer:
 

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Don't mind the 3.8 at all (I drive like your grandfather anyway), but I hate the slushbox. Did I mention that the transmission sucks? :)
 

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'07 X, 6 Speed, 22,000 miles

If you buy the six speed make sure you at least get the 4:10 gears. I didn't and regret it.

It's fine on the road. With 32" tires and basically no other mods I'm getting 18-19 MPG consistently.

Thing seems to stall off the line pretty easily.
 

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I currently drive a 7.3L PSD and a 6.0L V8 and drove another 6.0L V8 for 5 years.

I just drove a friends Sahara Unlimited with 35" Mickey T's and those that complain of the power, I just don't understand. While I am indeed getting a V8 conversion for my Rubicon done, there is no power issues with the 3.8L, IMO. Unless you are trying to compare the thing to some type of sports car or other vehicle with better than average power to weight.... the 3.8L is fine. And this is with 35s and 4.10s.
 

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I was happy with the power of my stock Rubicon. When I installed my lift and 35" tires, I was concerned about a loss of power and figured that I would need to regear in the near future. I was surprised that the power loss was barely noticable and will not be regearing now. I have no complaints about the engine and the 4.10 gears. Even with the bigger tires, it still puts me back in the seat off the line.

I have the auto, by the way.
 

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I'm a bit disappointed, but I maybe expecting too much. I have 35's and the 4.10 gears (auto) and I know I need to re-gear (5.13's in the works). I drive it like I stole it too. It does OK on power, above 2800 RPM. Below that it aint got enough power to pull a greasy string out of a ducks ass.

The part I hate is I'm getting piss-poor gas mileage. Worst tank has been 9.2 MPG and the best I've gotten in 13.8 MPG.

I friend of mine has a Commander with the HEMI, and the thing is a rocket-ship, and he gets around 17-18 MPG.

Come-on Jeep Corp. give us a HEMI and your CAFE standards will go up!!!
 

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I apologize in advance for the long post - if your eyes glaze over easily you might want to skip this one! :cruiser2: Here's the book I wrote on this issue on another forum:

This is an often discussed topic, so I went back and tried to consolidate my numerous posts on the subject.

When you compare the torque curves of the 3.8 and the 4.0 there is not much difference. Yes, the 3.8 torque peak comes at a higher rpm but it doesn't just drop off before the peak - the 3.8 is still an OHV, relatively torquey engine. While I agree that the TJ's 4.0 is a slightly more torquey engine (I had a XJ w/the 4.0 for a while so I'm familiar with it), I think a bigger difference between the drive feel of the TJ and JK is the gas pedal recalibration. A lot of TJ owners, particularly rock climbers, have complained over the years that the TJ gas pedal was too touchy - making it more difficult to negotiate slow, technical terrain. I am not a former TJ owner, but I've driven TJs offroad enough to agree with this complaint. You get used to it, but I always thought a true rock crawler should have a nice smooth/slow throttle. I think the JK throttle control is great - if you want it to go fast you've just got to lay into it quite a bit, which many people are not used to, particularly former TJ owners. Anyways, just goes to show you can't please everybody.

Also, the TJ is not a fast vehicle, but it does feel fairly fast, especially around town because it rides rough and is noisy. It is a visceral experience. Kind of like when I used to drive around in my buddy's Willys on the freeway. We were going 55 but it felt like 100. The JK is a little more refined to drive, so you don't get the same feel.

As for the 3.8 in general, I disagree with the OP. I've driven the 2-dr and I think the 3.8 is perfect for it. Power to weight ratios generally tell a pretty good picture about the feel of a vehicle. I did a quick comparison and the ratio of a 06 Rubi is 19.7. The ratio of a 07 Rubi (2-dr) is 20.4. So each JK horse is pulling a little more than an additional half pound. That is really a very small increase, but it will likely make the JK feel a little more sluggish than the TJ. Add the change in experience due to the raw nature of the TJ and the fact that most everyone has been driving and posting their experiences with 4-dr (which is even heavier when compared to the 06 Unlimited) hence the opinions that the JK is underpowered. Here is how the power to weight ratios of the Unlimiteds compare: 06 - 20.5, 07 - 21.4. Thus, the 2-dr JK should feel a lot like the 06 Unlimited in terms of quickness. The 4-dr. should feel a bit slower. To put all of this into perspective - the power to weight ratio of a 1942 Willys Jeep - 45.4 lb/hp.

I have a JK Unlimited Rubi Auto and I do think that it is slightly underpowered with the 3.8, but I think it is perfect for the Jeep and wouldn't upgrade unless it were a no cost option. It is relatively fuel efficient, it is an older, proven technology that is apparently easy to work on, and it is relatively torquey. I also agree that the engine (or computer program) loosened up considerably after 3-4,000 miles. It's still slightly underpowered, though - not much acceleration or passing power. For a car, that would be a major issue for me. For a Jeep, however, dependability, simplicity (for quick trail fixes), fuel economy (for long trail rides), and torque (for rock crawling and mud running) are much more important to me.

As for fuel economy, the JK is great for what it is in my opinion - the JK is not a minivan or a Dodge Stratus, it is a 4x4 convertible vehicle that is shaped like a brick with heavy duty running gear. When you compare the actual mpg numbers, the JK is actually pretty fuel efficient:

07 JK 4x4 Auto - 16/19 (city/hwy)
07 JK 4x4 Manual - 17/19
07 JK 4x2 Auto - 17/21
07 JK 4x2 Manual - 18/22
07 FJ Cruiser 4x4 Auto - 17/21
07 FJ Cruiser 4x4 Manual - 16/19
07 FJ Cruiser 4x2 Auto - 19/22
07 H3 4x4 Auto - 15/19
07 H3 4x4 Manual - 15/20
04 Dodge Caravan AWD Auto - 15/21

As you can see the JK holds its own in actual mpg comparisons. Yes the FJ has a more powerful engine with similar economy, but it is also slightly more aerodynamic, has less robust running gear, and comes with a more efficient 5 spd auto for the auto version. The tradeoff is the FJ engine is arguably more difficult to work on than the JK engine and requires premium fuel. Note the H3 numbers - similar numbers for similarly poor aerodynamics and strong running gear, but the H3 has a 5-cylinder engine and still can't beat the JK's numbers. I included the 04 Caravan, because that's the last year Dodge offered it in AWD and it has essentially the same engine as the JK. Note that the JK actually gets better mpg in the city and is not far behind on the highway.

The frustrating thing to me in reading a lot of the negative posts is that if Jeep really wanted to get an extra few mpg with the 3.8 they could have improved the aerodynamics further (more slanted windshield, no fender gaps, spare under vehicle, dropped various underbody components to improve airflow under the vehicle, dropped the vehicle to minimize underbody airflow, smaller mirrors, etc.) or they could have made the drivetrain more efficient (smaller, more efficient axles; 5 spd. auto). With the possible exception of a 5 spd auto (which probably was not added for cost reasons - I could also see that being added later, possibly in combo with a new engine option) Jeep did not make these changes because they wanted to increase the trail-worthiness of the Jeep as a first priority with increased fuel economy as a lower priority. We should be praising Jeep for keeping the Wrangler styling cues intact and making the drivetrain more robust for off-road conditions (which is what everyone on the forums was asking Jeep to do, by the way) instead of designing the JK for maximum fuel economy. Jeep did do some things, by the way, to increase fuel economy and has been berated for them in the forums, almost without exception (how many people on the forums praise Jeep for curving the windshield or installing the plastic air dam). Again, you can't please everybody. Sure Jeep could of improved the mileage by making the vehicle more aerodynamic and weakening the mechanicals, but I'm glad they didn't. They are offering a 2WD option, which improves mpg. If mpg is a prime consideration get the 2WD.
 

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Nice summary Cab 76. There is no vehicle that is all things to all people.
We can only judge by the brief time we've had it, but our JK is an improvement over our two TJs in quiet and overall driveability.
There are LOTS of non-convertible SUVs out there, especially if you are only doing the occasional off-pavement, that have better performance on pavement. However, if you want something that will spend a lot of time off-pavement, the Wrangler is the only Jeep.
 
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