The legendary 4.0

[AndyG]

The 4.0 is a legend . And a dinosaur. It is both loved and disliked .

Namely it is disliked by those in the know about modern engine weight and performance.

Why is it a legend then?

This is what I contend -

Back in the day , motors were considered shot at 100,000 miles and it’s 258cc predecessor would easily last twice that .

IN THE LAND OF THE BLIND, THE ONE EYED MAN IS KING.


I still like mine , I like knowing it will last and last , I like the torque , and I like the reputation it has . I’d like a lighter , more powerful engine even more .

 

[Chris]

I think for the purpose of off-roading it's a good engine with a lot of low end grunt. Compared to any modern engine it is a dinosaur indeed. However, maybe that's some of the appeal of it. It managed to stay around since 1965, which is pretty impressive.

 

[89grand]

What's even more impressive about the 4.0, is the next gen Wrangler (JK) motor was actually a lot worse...until 2012 at least.

 

[pagrey]

When the HO was released it had a pretty good power to displacement ratio. It runs for a long time and doesn't blow up. It has a large percent of total available torque available at idle, not 1500rpm, idle.

That's why legend.

 

[pagrey]

If somebody put a slant six or Ford 300 in a solid axle 4wd with air bags let me know.

 

[89grand]

If somebody put a slant six or Ford 300 in a solid axle 4wd with air bags let me know.

You'll want to to do something with the distributor if you use the Slant 6.

 

[Flivver250]

The basic design is quite similar to Chevrolet's 6 cylinder which has been around since 1929. Chevy never used the flathead. All the cutting edge technology you would expect from Lincoln logs. It may not be a big powerhouse, but its simplicity makes it the perfect choice for folks who desire reliability and the ability to fix on the fly. Enough grunt to perform most of the tasks required, just not designed to win races.

 

[LittleTankTJ]

Mine has broken 200,000 miles and just... Goes. So many parts have just worn out, but the 4.0 keeps chugging. New fuel pump, new spark plugs and it acts like a new engine.

But when it finally does go, I have to decide if I put a new one in or the modern day equivalent. If this vehicle was to be made today, what would go in? It honestly wouldn't be something exotic or super high powered. That wasn't what our Jeep's were.

 

[coherent]

What's even more impressive about the 4.0, is the next gen Wrangler (JK) motor was actually a lot worse...until 2012 at least.

I agree. I had a JK and while it was a smoother running motor and the gas mileage was tons better, the lack of torque when paired with the 6 speed manual was really terrible when climbing hills at highway speed.

 

[JEEPCJTJ]

If somebody put a slant six or Ford 300 in a solid axle 4wd with air bags let me know.

The other two great inline sixes which both were used in 4wd vehicles. Who needs airbags?

I also have wonder how many 4.0s and it's relatives hit an early death thanks to cash for clunkers.

 

[BryantJT]

Personally if the 4.0 was to give up, I'd probably get the 4.6 stroker kit. https://golenengineservice.com/jeep-engines/

 

[Kentj]

I like the 4.0 *because* of its simplicity, its low-end grunt, proven longevity and availability of parts and upgrades.

I bought a TJ 4.0/5-spd specifically for those simplicity and rugged construction aspects. The fact that it has only 1 computer means that there is a pretty darn good chance that I can easily keep it running and maintained in my own garage for a few decades more if I choose. I like that feeling.

As nice and powerful as the new JL motors are, they are complex (and thus sometimes fragile) beasts due to increasingly demanding EPA regs. I still will likely own a JL someday, but I know I'll miss the simplicity of the TJ and its 4.0 when that day comes.

I think for the purpose of off-roading it's a good engine with a lot of low end grunt. Compared to any modern engine it is a dinosaur indeed. However, maybe that's some of the appeal of it. It managed to stay around since 1965, which is pretty impressive.

 

[Goatman]

Every I-6 engine has been really good to grate. The Toyota engine that the rest of the world uses is awesome. The Nissan and Porsche 6's prove they can handle massive RPMs and induction. The Ford 300 is better than their 302. Only GM has no I-6 of legendary fame. I think that is only due to the great small block V-8 overshadowing it. I've had 2 Chevy I-6 vehicles. While certainly less powerful than some other brands, I never had a lick of problems with either. 1 a Mustang, other a PU.

 

[Chris]

I like the 4.0 *because* of its simplicity, its low-end grunt, proven longevity and availability of parts and upgrades.

I bought a TJ 4.0/5-spd specifically for those simplicity and rugged construction aspects. The fact that it has only 1 computer means that there is a pretty darn good chance that I can easily keep it running and maintained in my own garage for a few decades more if I choose. I like that feeling.

As nice and powerful as the new JL motors are, they are complex (and thus sometimes fragile) beasts due to increasingly demanding EPA regs. I still will likely own a JL someday, but I know I'll miss the simplicity of the TJ and its 4.0 when that day comes.

Couldn’t agree with you more! Well said!

 

[Equilibrium31]

What's even more impressive about the 4.0, is the next gen Wrangler (JK) motor was actually a lot worse...until 2012 at least.

Yea, I remember test driving a JK back in '07 before I bought my TJ. The extra torque from the TJ made it so much more enjoyable to drive that the choice between TJ/JK was a no-brainer for me.