How difficult is it to swap out the 2.5 for the 3.9 in a '00 Dakota Sport? This is the first time I have attempted anything like this and would like to know what I am getting myself into.

Will I need to replace the wiring harness? Will the engine be compatible with the 5 speed manual tranny that is in the truck? Will I need to change motor mounts? Any and all information will be greatly appreciated.

 

alot will be different. motor mounts for sure will be (I4 to V6), PCM will be different, wiring harness will be different, Not sure if trans will work or not.

 

What Magnet said,

Plus you probably have the AX-15 tranny, but if you have the NV3500 then I believe it'll bolt up just fine.

But you will need new motor mounts, wiring harness, PCM.

 

Actually, it should be the NV1500 that you have. It won't handle the torque - the NV3500 will bolt up.

 

Yep, you'll need not only the new engine, but new computer and wiring harness to go with it as well as a matching transmission. Then you'll have to figure out your motor mounts.

It's the exact same work to swap in a V8 other than plugging in the harness to 2 extra injectors. I would skip the v6 and do a v8 swap unless you already have the 6.

 

Probably other stuff like the fuel system as well (fuel pump, fuel pressure regulator, larger gas tank.) And of course, when you go to the correct trans, you'll need a driveline and maybe different linkage. Front suspension? Rear end (gearing?)

Can you find a parts truck? You'll really need one.

Is your 4 cylinder dead? You might be ahead financially to dump the 4 cylinder truck and get what you want. Seems to me like you're looking at a whole lot of work time, down time, and expense to get a performance bump.

 

I agree. You'd probably be money ahead to sell the 4 cyl truck and just buy a 6 or 8 cyl truck.

Now if you could find a truck witha good drivetrain that had been rolled and the body was trashed but the engine, transmission, transfer case, drivelines, ECU, and everything that go with them was good then you might be able to do this project at an affordable price.

I don't know if you will need a new fuel pump or not. Worth looking into though. You would probably be fine with your rear end to go to a 6 cyl. And typically 4 cyl trucks have lower gearing then the bigger engine versions, so you might actually have a nice little setup if that is the case. I know in Wranglers the 4 cyl models come with 4.10 axle gearing and the 6 cyl ones can be as low as 3.07. Also, you will need to find out if your exhaust will mate up to the existing exhaust on the 4 cyl. I'm sure there are other things that will pop up too.

Is the radiator in the 4 cyl trucks the same? Will it keep up with a bigger engine?

If you don't want to sell the truck another option would be to just change the axle gears. That might give you the performance increase you're looking for. What axle gear ratio do you have now?