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Old 05-27-2009, 06:23 PM   #1
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3.8 vs. 4.0 ???

Why did they change to a 3.8l I-6 over the great 4.0 ??? I've been rather curious about this for a while and thought I'd bring it up.

Any ideas and/or opinions on the pros and cons to each engine ????

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Old 05-27-2009, 06:38 PM   #2
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A far as my knowledge they couldn't make the 4.0 work with current emission standards... I can only imagine what obama and fiat and the treasury secretary will do to the future of the Wrangler, one thing I know is they can keep their paws off my TJ!

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Old 05-27-2009, 06:41 PM   #3
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There are numberous reasons. Fuel economy, horsepower, they used it in other product lines, etc.....

It's a good motor. The torque and horsepower curve is a bit higher than the 4.0 in the RPM range. I still like the 4.0 better just because it's a 250,000 mile plus motor. The 3.8 has only been in the wrangler for 3 years now, so we'll see what changes they make to it.
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Old 05-27-2009, 07:36 PM   #4
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i love this debate, do a search, there's some great arguments.

and the emissions is a bs excuse, 4.0 was pretty good on emissions. its just a bogus excuse they use when obsoleting the beloved motor. i love the all cast iron, straight six engine. been on the same platform for freaking half a century or so.

3.8 has proven to be a solid motor, its been in the minivans for at least 20 yrs. but it just doesn't do it for me.
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Old 05-27-2009, 07:40 PM   #5
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It's a good motor. The torque and horsepower curve is a bit higher than the 4.0 in the RPM range.
The 3.8L's torque is actually lower in the lower rpms than the 4.0L is and that's where it counts. The 3.8L is a better highway engine but the 4.0L is a better offroad and around-town engine. Longevity-wise, as you said Jack, the 4.0L wins hands down.
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Old 05-27-2009, 07:43 PM   #6
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My 4.0 passed emissions without a hitch, and not once but twice.
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Old 05-27-2009, 08:09 PM   #7
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I haven't done any reading on the 3.8, but I assumed it was a V6. Is it an I6?

I'm sure it's aluminum too.
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Old 05-27-2009, 08:13 PM   #8
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v6 cast block aluminum heads
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Old 05-27-2009, 08:45 PM   #9
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v6 cast block aluminum heads
That's what I thought. The first post said I6 though.
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Old 05-27-2009, 10:31 PM   #10
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235 at 3200 for the 4.0 and 237 at 4000 for the 3.8. With something like 60% of the 4.0's coming right off the pedal at 1500 rpm.

I've been around the new 3.8 a lot and it is a great motor. However I'm not sure that it can hold up to many performance mods. Plus the computer control is taking over the world.
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Old 05-28-2009, 06:37 AM   #11
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Damn, my bad....3.8 V-6......not I-6.

Meth is a helluva drug !! haha just kidding....
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Old 05-28-2009, 11:40 AM   #12
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235 at 3200 for the 4.0 and 237 at 4000 for the 3.8. With something like 60% of the 4.0's coming right off the pedal at 1500 rpm.

I've been around the new 3.8 a lot and it is a great motor. However I'm not sure that it can hold up to many performance mods. Plus the computer control is taking over the world.
I don't know about hold up to mods, but there is almost no point in putting performance mods on the 4.0L.

I love my 4.0L. I wouldn't trade it for anything. I do believe that the 3.8 gets better gas mileage which is one reason Jeep went with the motor. Correct me if Im wrong though.
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Old 05-28-2009, 03:22 PM   #13
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Our 99 T&C van has the 3.8. 81K and so far so good. My 09 JK with 500 miles has the same, of course. 500 miles and so far so good. The 84 CJ I had way back had the 4.2 and did not impress me much. Although I think that was also in the 82 J10 and other than being under powered (4 sp and HEADERS no less) it gave me no problems.

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Old 05-28-2009, 04:51 PM   #14
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The switch to the 3.8 in the JK was purely to save money. If you are struggling and facing bankruptcy it made sense to eliminate one motor on the production side. Unfortunately they eliminated the wrong motor. I've owned 8 jeeps over the last 16 years (CJ-7s, YJ's and TJ's) and every one of them had the 4.0 motor. It's the biggest reason I haven't traded my 2000 and 2003 TJ's in on a JK. I can't leave a legendary motor for a motor that has been rocking the Dodge Caravan for a couple of decades.

It's all the more reason to just take care of your TJ's and keep them as long as possible. Hopefully Fiat will start enough of a recovery for Jeep to get the 4.0 reinstated. There are a lot of reasons my parents have to trade their Caravan in for a newer one every few years. And the 3.8 V-6 is responsible most of the time. If Jeep owners make enough noise about the direction the Wrangler is going, maybe the right people will listen. Jeep needs it's durability and reputation back. You just shouldn't screw around with the kind of loyalty we Jeep owners have.
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Old 05-28-2009, 04:55 PM   #15
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The reason that Jeep Engineering stated was that the 4.0L engine wouldn't meet the upcoming Federal emissions standard, and that it was shorter (a V6 is shorter than an I6) which meant it helped them meet tougher crash worthiness standards.

If anything, the 3.8L V6 is more expensive to produce than the 4.0L due to most of the 4.0L's tooling having been paid for at least 20 years ago.
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Old 05-28-2009, 05:10 PM   #16
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It's all the more reason to just take care of your TJ's and keep them as long as possible. Hopefully Fiat will start enough of a recovery for Jeep to get the 4.0 reinstated. There are a lot of reasons my parents have to trade their Caravan in for a newer one every few years. And the 3.8 V-6 is responsible most of the time. If Jeep owners make enough noise about the direction the Wrangler is going, maybe the right people will listen. Jeep needs it's durability and reputation back. You just shouldn't screw around with the kind of loyalty we Jeep owners have.
I don't think the Wrangler is going in the wrong direction at all. No one has any idea how that motor is going to hold up in the 200k range in the Wrangler. Drive by wire is a reality in all cars now along with TPMS etc..... Chrysler had to move Jeep to that level of control also. The wrangler is still on Chryslers low end for emissions and fuel economy standards which is fine with them because they have produced enough cars to keep them on the level.

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If anything, the 3.8L V6 is more expensive to produce than the 4.0L due to most of the 4.0L's tooling having been paid for at least 20 years ago.
That's for sure Jerry. That motor has been produced in the old Toledo plant for something in the neighborhood of 30+ years. Jeep definitely knew how to build a long block 6 and do it on the cheap.
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Old 05-28-2009, 05:14 PM   #17
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3.8 has been in production nearly as long.
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Old 05-28-2009, 05:17 PM   #18
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The V-6 being shorter makes since along with the emissions statement. My gut feeling is that once the JKs are out on the road a couple more years and we get more Jeeps hitting the 70k or 80k mile mark, we may have a group of unhappy Jeep owners. I hope I'm wrong. I just keep thinking about the dozens of people who have stopped me in my Jeeps over the years saying they always wanted to own a Jeep. And they always mention the good things they hear about the I-6. The solid reputation is there for a reason. In spite of the Compass and Patriot.
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Old 05-28-2009, 05:18 PM   #19
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3.8 has been in production nearly as long.
Not in its current configuration with all of the computer controlling that is involved.
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Old 05-28-2009, 06:40 PM   #20
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4.0 went from renix to h.o. to direct ignition w/ ram intake.
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Old 05-28-2009, 06:46 PM   #21
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4.0 went from renix to h.o. to direct ignition w/ ram intake.
Mmmmm, renix... Everyone has a bad design day every now and again.
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Old 05-28-2009, 06:56 PM   #22
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renault and bendix sure made a gigantor improvement over the 4.2 of the late 80's. and i had one in an xj, and my mj is a renix. i've seen worse.......ford.

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