Why no engine in the new jk ?

wendell · **Posted:** Tue Dec 12, 2006 9:16 am

You would think with all the time chrysler had to prepare for the new wrangler, they could of done better than a mini van engine. It's been reported for several years now, that the 4.0 I-6 was going to be phased out. Every test I've read so far has the engine as the weak link. The nitro has the 4.0 v6, why not jk, won't it fit ? At least the 3.7 would of been better, won't it fit either ? It seems like some poor planning, they would have been better off to keep the tried and true 4.0 I-6 a round a lttle longer if the 3.9 is the best that they could do. This can't be the motor thier going to stick with. You would think they could release the motor and wrangler at the same time with years to plan it. Unless they are going to stick with the 3.9 and that would just plain suck and I'm sure will hurt sales once the newness wears off.

pixeldzn · **Posted:** Tue Dec 12, 2006 10:25 am

From what I've heard it is in fact a stopgap engine for the Wrangler, which will be one of the first to recieve the new v6 that Chrysler is developing. I think the choice to use the 3.8 came from supply line availability, and you would be real surprised how that engine performs when tuned for a 4x4 and in front of 4.10 gears.

Big D · **Joined:** Mon Jun 05, 2006 10:08 pm **Posts:** 349

As the previous post said. This is an instock engine. It is a minivan engine. It's been around for a while so reliabilty problems are small. They pretty much though why fix something when it's not broken. A JK will be put through a lot more stress than a Nitro, so a decision was made to go with one in stock (to limit retooling and startup costs) and prevent reliabilty issues.

zeero · **Posted:** Wed Dec 13, 2006 8:14 pm

As said.....YES I was VERY surprised and VERY pleased with how my JK Unlimited Rubi performs behind the 4x4 and 4.10 gearing and on Dana 44's with 32" MTs being pushed around on it.......what a smooth ride. Very quiet, but man has it got BAWLS when its needed in 4LO....WOW....the amount of torque coming out of this blew my mind when in 4LO.

Nope, I think its great motor for the new JK, regardless of their reasoning behind using it. Its spec'ed up perfectly for its intended purpose.

:wink:

Brigrat · **Joined:** Sun May 21, 2006 6:17 pm **Posts:** 92

the 3.8 is one of the best engines Chrystler ever made. Ask some minivan owners, it is a great engine!!!

wendell · **Posted:** Thu Dec 14, 2006 3:41 pm

Every test that I have read so far has complained about the engine and lack of lowend torque. If they were going to use an engine that they allready have, then why not just use the 4.0 I-6. It's famous for it's lowend torque and reliability. That why it makes no since. They allready an old tried and true motor. The 4.0 is legendary and loved and admired and is allready missed. With out some new motor wow us with, it sure doesn't seem like a smart move. Any ohv engine is on barrowed time anyway, why not just use the 4.0 untill they built a better replacement ?

alljeep · **Posted:** Thu Dec 14, 2006 4:13 pm

wendell wrote:

Every test that I have read so far has complained about the engine and lack of lowend torque. If they were going to use an engine that they allready have, then why not just use the 4.0 I-6. It's famous for it's lowend torque and reliability. That why it makes no since. They allready an old tried and true motor. The 4.0 is legendary and loved and admired and is allready missed. With out some new motor wow us with, it sure doesn't seem like a smart move. Any ohv engine is on barrowed time anyway, why not just use the 4.0 untill they built a better replacement ?

In general, an I-6 configuration is up to 30% less efficient than a V-6 configuration for a gasoline engine depending on the vehicle it goes into. The new wrangler grew in size and weight and the fuel economy numbers would be horrible. Real world economy for driving a stock '06 Unlimited Rubi with the 4.0L in city traffic yields about 10-12mpg - same engine in a heavier and larger rig would be crazy low. It's inefficiency also means it can no longer meet tightening emissions requirements. In reality, it's the older generation 4.2L I-6 that is legendary with it's low end torque.

The 3.8 V6 does very heavy duty service in the mini-van market. It hauls full loads of people (7+) and tows campers at the same time with little failure before 150k miles. When you have the gearing in 4x4 low from the t-case of a rubicon, the torque rating becomes of very low importance in the overall picture. Even the gear reduction in the standard t-case is more than enough.

I suspect folks might complain about acceleration performance in an '07 4-door Unlimited automatic with 3:21 rear gears instead of the 4:10s when comparing to the performance of a normal car.

Jeger · **Posted:** Thu Dec 14, 2006 4:32 pm

I've got a town&country with the 3.8 in it. I dont think I would have any complaints about that engine, it will get up and move, for a minivan anyhow. Will light the tires up everytime if you stomp on it. Even with traction control. We have been pretty hard on ours and it is still going strong at something like 180K. 3:21 gears would kind of suck for a jeep though. Is that what they have?

wendell · **Posted:** Sat Dec 16, 2006 9:06 am

I beg to differ, the 4.0 is legendary as well, the 4.0 has the lowend torque of the 258 with a lot more horse powernd will last 300,000 miles with proper oil changes. The big upgrade now for 258 owners is to install a 4.0 head and efi. The 4.0 was derived from the 258 and the crank can be used for a 4.0 stroker. To each his own, but the last real jeep wrangler was made in 06. This new chrysler hummer looking thing doesn't have much real jeep left in it. I'm just glad there are plenty of tj's, yj's and cj's still a round. As the insiders report, chrysler is on suicide watch and won't be around with in the next 10 years anyway if things don't change. So I guess the good thing is that they can't destroy jeep to much more without destroying themself's. I don't mean to sound negitive, but I've owned jeeps from the willys era to now, and I just can't get excited about the direction it's headed. The jeep brand allways stood out as it's own vehicle, now there so mixed up with dodge, you don't know if your getting a jeep or a warmed over dodge with a jeep grill. I've tried to be positive, but I'm old school and remember quit well how jeep use to be, nothing to fancy, but tough as nails, a no nomsense 4x4. Forget what I said about the 3.8, it's fine. I'm just a jeep purest that long for the good old days, when there were straight 6's and you could fix them with baling wire and duct tape ha ha.

zeero · **Posted:** Sat Dec 16, 2006 12:18 pm

Well owning this JK Unlimited....I have put in 4LO with lockers on....and I have to say, the amount of torque flowing out of this DOUBLES what my Liberty has EASILY....and quite honestly....the meer touch of the skinny and I was lurching forward like I'd never driven before.

TONS of torque....and quite honestly a VERY scary amount of it....extremely surprising and VERY VERY touchy.

Returning to 4HI and 2HI.....the torque easily cut down to HALF of what it has in 4LO.

Just staggering amounts of torque in 4LO......

Yeah, this motors good....regardless of what arm chair critics think.....I own the thing and I've been doing this stuff for 10 years....and never have I felt that much torque in 4LO come out of a stock vehicle, not even in Land Rover.

Of course, its the gearing and all.....but you need a good motor to combine with the gearing or you have nothing......yeah, I'm fully impressed.

Speaking of gearing, Jeger, the JK has 4.10. :wink:

Being the owner and one who drives it EVERY day since I got it.....I think that carries some weight.

:wink:

wendell · **Posted:** Sat Dec 16, 2006 2:46 pm

Lets be a little more serious, a fat head willys 4 cylinder has tons of torque or the feeling there of in low range with 5:13 gears. I haven't had a 4x4 yet that didn't have gobs of torque in low range except my samuri, it was a little light in lowrange, not bad, but could have been geared a little lower. Most wranglers won't have 4:10 gears and 4 to 1 t-cases, or will most of thier time be spent in 4lo. I'm sure they grade it on all a round performance. I'm sure it will be fine, times change. It really doen't matter to me, I'll never own one anyway. I just figured more people would mis the 4.0, I guess not, so wheel away.

Jeger · **Posted:** Sun Dec 17, 2006 8:11 am

I am a fan of the straight six myself, and a supercharged or turbo straight six is a very powerful engine in most cases. I dont know much about the efficiency and stuff, but in a lot of cases where sheer power is the goal, an inline engine is what is used. Think of heavy equipment and semi's.

wendell · **Posted:** Sun Dec 17, 2006 8:32 am

I don't think a little more weight is the issue, they used the 4.0 in GC for years without a problem. Golden puts out a 4.6 stroker thats good for 260 hp and allmost 300 foot pounds, add an avenger super charger, and you would have an awesome 4.0. I can't say I'll miss it, cause there is still so many a round. Thier will be another one in my driveway before long, Lord willing. I'm looking to get a 4.0 powered yj next.

alljeep · **Posted:** Tue Dec 19, 2006 9:15 am

wendell wrote:

I've tried to be positive, but I'm old school and remember quit well how jeep use to be, nothing to fancy, but tough as nails, a no nomsense 4x4. Forget what I said about the 3.8, it's fine. I'm just a jeep purest that long for the good old days, when there were straight 6's and you could fix them with baling wire and duct tape ha ha.

I hear ya, trust me, I hear ya... I'll throw a few pictures in here of my lost but not forgotten favorite Jeeps of all time. Here is my first. It was a 1962 Willys CJ-6 (rare 101" wheel base) with all original drivetrain. It had the original Spicer 25 front and Dana44 rear with the factory 5:38 gears. Couple this with the factory twin stick transfer case and the original F-134c.i. (90hp) engine had plenty of gearing to go anywhere.

Here is my other favorite. It was my 1974 AMC CJ-6 (ultra rare 104" wheel base) with it's original 258 I-6 engine, original Dana 44 rear and Spicer 25 Front with 3:73 gears, Dana 20 T-case, and original HD optional T-15 3-spd transmission. They only made CJ-6 models from 1955-1975, and the AMC motors did not come into play until 1972. With about 1200 produced per year I was shopping for a CJ-6 made in only a 4 year span and I found it! (of course now it's gone :cry:

).

Here they both were back when my wife and I were DINKS (double income no kids):

These jeeps were numbers matching originals and my favorite of all time is the 258c.i. I-6. But times have changed. I have kids now and have had to move on to things I can maintain and take the family along in safely.

I test drove a 2005 Unlimited with the new 6-speed manual right when they first hit the dealer lots in October of 2004 out here. Man did it ever bring the fond memories of the I-6 back. The sound, the feel, everything. I love em...

What I meant about the 258 being the legendary low end torque was that when it came out in 1971 it produced it's max torque of 240 ft-lbs(gross)/195 ft-lbs(net) at a mere 1800 rpm.

When the 4.0 came out, it produced it's max torque of 220 ft-lbs(net) at 4000rpm.

Now, what I suspect is that the 4.0 has a VERY broad and flat torque curve, so I think it is still producing as much torque at 1800rpm as my old 258 was. So they are both legendary for the time they were produced and the technology involved.

alljeep · **Posted:** Tue Dec 19, 2006 9:32 am

Jeger wrote:

3:21 gears would kind of suck for a jeep though. Is that what they have?

Most of them have 4:10 gears. But certain X (and maybe some Sahara) models have the 3:21 gears. Anything with a tow package forces 4:10 gears. And I think anything with an automatic transmission forces 4:10 gears. Jeep has changed their options several times the first few months the new Wrangler was produced, but the 3:21 gears are definitely available in manual transmission lower spec vehicles.

wendell · **Posted:** Tue Dec 19, 2006 9:59 am

Alljeep, "now", those are jeeps !!!!!!!!!!!!!!!. I still get a thrill out of rididing in an old 60 hp flat fender with 5:13's, suck on the highway, but such a balst on the trails. Those old jeeps are what jeepin is all about. A low budget and a beat up jeep, nothing like the high whine od a jeep 4 banger in low range. The straight 6's had a distintive sound as well. That why the jeep hobby is so great, you have 66 years of great vehicles to choose from and a good deal of them are still in use. My first jeep that I personaly owned, was a 75 CJ-5, 258 and a 3 speed, an awesomw trail machine. I grewup arond the flat fenders back in W,Va on the farm that belonged to the family, a lot of them are still around today and are fired up every deer season. My tightwade cousins won't give me or sell me one, the b**stards ha ha !

SnowgodCCR · **Posted:** Sun Dec 31, 2006 8:42 pm

It's not that the 3.8 is lacking in torque, it's just that it's torque is available at about 700 RPM higher than the 4.0 I6's torque was. It's not a big deal at all and you don't even notice it offroad.

asgates · **Posted:** Tue Jan 02, 2007 9:02 pm

the 3.8 may lack in the low end torque, but it won't be long until someone does a "bowtie 350" swap in a JK. i actually have a buddy who just bought a JK a few weeks ago and is now in pursuit for a 350 block to stroke out to a 383. until then, he feels that the 3.8 is plenty reliable and works well with the stock gearing.

zeero · **Posted:** Wed Jan 03, 2007 5:19 pm

SnowgodCCR wrote:

It's not that the 3.8 is lacking in torque, it's just that it's torque is available at about 700 RPM higher than the 4.0 I6's torque was. It's not a big deal at all and you don't even notice it offroad.

From driving it almost a couple time a week on the trails...I'll tell you all, there is certainly no lack in torque AT ALL....

I own a modded Liberty and the 2007 Rubicon.....and it has PILES more torque than the Liberty....so much its actually a little scary....

There is certainly no lakc in torque....the gearing and motor combination are perfect as far as I'm concerned....

Nice work Jeep....you've doen good things with this truck. :wink:

wendell · **Posted:** Thu Jan 04, 2007 8:48 am

Some of you guy's can't be serious, I test drove one yesterday with the manual tranny, all most stalled it a couple of times, it is certainly lacking in lowend torque compared to the 4.0. The only time it wasn't noticable was in low range, how much of our time do we spend in low range ? It had plenty of power, it just hit higher in the rpm range, it's no 4.0. In all fairness, it wasn't as bad as I thought it might be. Even so, those old cam in block motors are on thier way out, so don't look for that motor to be the main offering for to long. I say the new 4.0 will work it's way into the jk, a long with the crd v-6. However the 4.0 may have different cams for better lowend, they may even detune it a little, DC may feel 260 hp is a bit much for the lighter weight jk. Even the 4.0 yj and tj had 10 less hp than did the 4.0 cherokee's, 180 hp to 190 hp prospectivly.

Why no engine in the new jk ?

Who is online