Pirate 4x4 banner

Has anyone kept the 4.0 in their crawler?

2K views 41 replies 25 participants last post by  84 Sheepdog 
#1 ·
I have to swap engines and I have a line on a cheap 4.0/AX15 combo to replace my 2.5L. I never really read about anyone keeping the 4.0 after doing a buildup. Why is that? Just lack of power or the 4.0 is just not a good engine for crawling?

Thanks
 
#3 ·
Well, I'm certainly not as hard core as the guys on this board, I guess, but currently I'm planning on keeping my 4.0. I think it makes a great rock crawling motor.

Keep in mind that I'm keeping my 4.0. That is not the same as swapping one in. The biggest reason I'm keeping it is because it's there, runs perfectly well, and provides more than enough power for what I want to do. If, however, I had to swap motors for some reason, I personally would probably go the sbc route.

Having said that, the 4.0 is a reasonably powerful, tourquey, trouble free engine. starts all the time. idles like a champ over obstacles. never burns oil. never gives me one once of grief.

the 'idles over obstacles' thing is often overlooked, I think. One person who has a 5.0 ford swap done told me he had a lot of problems maintaining control because even the slightest throttle input sent WAY too much power to the rear wheels. From my motorcycle roadracing days I know that there is such as thing as too much power, in that if you cannot dial in the amount of power you want (between 0 and the maximum available) then the power is not tractable and may overwhelm your available traction.

I find this happens with V8 guys. As soon as they get a V8 they tend to use tire spin a lot more. Could just be cuz it's fun. Anyway, my point is the 4.0 is a very tractable, controllable engine. That's not to be undervalued,IMHO.

Also, less power means less breakage, all other things being equal.

On the negative side, another buddy doing a 5.0 swap discovered that the 5.0 ford V8 is about the same weight as the 4.0 - which means the 4.0 is not saving you anything in terms of weight. And I'm basically unimpressed with most horsepower gaining mods available right now.

All my 2c. And if I had the money, I'd probably go V8 for the same reason most other people do - because I COULD, and because it's FUN.
 
#5 ·
The Rockslut said:
I have the stock engine and tranny in my 94 YJ. 4.0/999 I have full width axles and 39.5" TSL's I love it. Could have more power but that will come in time, but I love the gas mileage
What mileage do you get? And what gears you running.

Thanks!
 
#8 ·
Well, don't want to disagree or anything, but the 4.0 is rated for around 17 mpg (imperial gallons) stock. That might equal 20 miles/us gallon, stock. But those ratings were extremely optimistic - I've rarely seen mileage that good in either my YJ when it was stock or now highly modified, or at any time in my bone stock cherokee. I find the 4.0 to be a bit of a hog.

HOWEVER, we recently went on a run with a 4.0, a stroked 4.0, and a 304 V8 in reasonably good shape. The highway killed the V8 - 3.55 gears, I think, 33 inch tires, auto tranny. That thing sucked like 3/4 tank getting to the trail head. I went through less than 1/4, the stroked 4.0 slightly more than 1/4.

Bottom line I guess is that any fuel injected motor is probably going to do better mileage wise than a carb'd engine generall speaking, but when comparing fuel injected motor to fuel injected motor, I suspect my friend with the 5.0 swap is going to end up getting better mileage than my stock 4.0, because it is going to take less effort for the V8 to push big tires.
 
#9 ·
One major disadvantage that no one else listed is length, swapping to a V8 or V6 can gain you quite a bit more drivetrain/driveshaft length, be it for doublers, long tranny's or longer shafts (or all the above).

That said I'm far (real far) from hardcore like some of these people, but I'm currently building my jeep, and plan on keeping the 4.0 for quite a while, just a good strong engine. Power isn't anything like a good V8, but the new 4.2/4.0 hybrid stroker kits are really intreging, and may convince me to hold onto the 4.0, when it comes to rebuild time.

Chad
 
#11 ·
ChadLloyd said:
Well, don't want to disagree or anything, but the 4.0 is rated for around 17 mpg (imperial gallons) stock. That might equal 20 miles/us gallon, stock. But those ratings were extremely optimistic - I've rarely seen mileage that good in either my YJ when it was stock or now highly modified, or at any time in my bone stock cherokee. I find the 4.0 to be a bit of a hog.

HOWEVER, we recently went on a run with a 4.0, a stroked 4.0, and a 304 V8 in reasonably good shape. The highway killed the V8 - 3.55 gears, I think, 33 inch tires, auto tranny. That thing sucked like 3/4 tank getting to the trail head. I went through less than 1/4, the stroked 4.0 slightly more than 1/4.

Bottom line I guess is that any fuel injected motor is probably going to do better mileage wise than a carb'd engine generall speaking, but when comparing fuel injected motor to fuel injected motor, I suspect my friend with the 5.0 swap is going to end up getting better mileage than my stock 4.0, because it is going to take less effort for the V8 to push big tires.
Thats cool. My rig pulls that mileage all day long any day of the week. If I put my foot in it it sucks the gas. I have a 91 MJ 2wd 4.0/AX15 that gets 20 mpg or better. Just sips the gas.
 
#13 ·
attachcurrie said:


What mods have you done and how much did it improve it?
My own is bone stock, I like it that way. But being surrounded by jeeps I've seen most of the usual gammit of mods - headers, K&Ns, etc - most of which seem to me to do very little.

BillaVista has a stroker, and while I'm impressed with the horsepower gain, I personally (no offense Bill) am unimpressed by the hassle required to get it, and get the motor running smoothly on pump gas. Just seems like you can get a lot more bolt on horsepower for SBC or Fords than Jeeps.

I'm not sure I would feel comfortable with Nos, turbo charging (too much change in tourque characteristics, which are primary plus to engine in first place), or supercharging, although I'm sure they would all result in dramatic gains in hp.

The length issue is a very good point, buddies 5.0 swap really cleared up some engine bay room!

My point of view is if you have a 4.0, keep it, and keep it stock. if you need more power, go SBC, but right now I personally don't need more power.
 
#15 ·
Just a thought , but smog? nobody has mentioned that. a 2.5 to a 4.0 in a wrangler is a legal swap with no hoops to jump through at the ref. station.
The 4.0 has repectable torque and i also get between 16 and 19 mpg.
all i'm sugesting is if you live out of state and your swapping in a engine that didn't come as an option for your ride you better do it right or have someone that will :zzz: while smoging it.

Not to far in the future of smog rugulations will clamp down even harder on that.


I'm a licienced smog tech and this is the advice that i give my freind s and anyone else who asks.


my .02

mike
 
#16 ·
The Rockslut said:
I was running 4:56 gears with 38.5" SX's and now have 5.13 gears with 39.5" TSL's.

Not sure of the exact mileage but it is around 20 mpg. Sucks more going up the freeway to the Con.
How are you getting 20 MPG with 5.13's and 38.5's? thats what I was getting when my rig was stock! now I get 15-16 mpg with 4.56's and 33" tsl radials. I think you need a new speedo gear dude.
 
#17 · (Edited)
SCORPION said:


How are you getting 20 MPG with 5.13's and 38.5's? thats what I was getting when my rig was stock! now I get 15-16 mpg with 4.56's and 33" tsl radials. I think you need a new speedo gear dude.
Sorry DUDE! DO you want to drive my rig and see what mileage it gets? First off i had 4.56's and 38's not 5.13's. So your junk sucks gas and mine doesnt. I drive my rig all the time and know what mileage it gets. I would now if my speedometer was off. I dont cruise down the highway in the slow lane with my speedo at 85mph and thinking i am getting geo metro gas mileage.

Besides I have another rig (if you would have read) that has a 4.0 and pulls down 20mpg around the city, even better on the highway. Wanna drive that one too? Wanna come check out my speedo gears? !:rolleyes:

I think you need to go away!
 
#19 ·
A lot of people kepp the stock engines because you rarely need the full power of it anyways when crawling.

You brake stuff easy enough with the stock engine.

That is if you are crawling.

Muddin is different. :D
 
#20 ·
I still run a basically stock 4.0 in my rig. It's decent, torquey, doesn't burn oil, I always know it's gonna start (but I don't get close to 20 mpg):p

When I blow it up eventually, I'll replace it with a SBC or Ford. I probably wouldn't pay to go from a 2.5 to 4.0, though.
Dion
 
#21 ·
Wow - I'm kinda jealous. I'm lucky to get 14 MPG. Granted, I've got an auto with no overdrive, but even stock I was only getting 16. Oh, well, what do you expect when you're basically pushing a barn door through the air? :)
 
#22 ·
I made the choice to go with a 4.0 over a V8 for many reasons.
1. Had one before in an XJ, loved it very dependable
2. Length of drivetrain, as stated above. The 4.0 was a bolt in swap for my 4.2 a SBC would have made my driveshaft about 4" keeping the stock CJ-5 wheelbase of 84"
3. Cost by the end of my swap I will have only spent about a grand including the motor. Got it for $400.
4. Did anyone mention the fact that they run forEVER!
5. Last but not least. ITS A JEEP PRODUCT, and I like that.

And I actually kept it OBDII
 
#23 · (Edited)
The Rockslut said:


Sorry DUDE! DO you want to drive my rig and see what mileage it gets? First off i had 4.56's and 38's not 5.13's. So your junk sucks gas and mine doesnt. I drive my rig all the time and know what mileage it gets. I would now if my speedometer was off. I dont cruise down the highway in the slow lane with my speedo at 85mph and thinking i am getting geo metro gas mileage.

Besides I have another rig (if you would have read) that has a 4.0 and pulls down 20mpg around the city, even better on the highway. Wanna drive that one too? Wanna come check out my speedo gears? !:rolleyes:

I think you need to go away!
calm down slut! I just thought it was strange thats all.

Oh ya and you got the 39.5's and 5.13's not 38's and 4.56's, my bad.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top