I have 2 possible used engine choices, a 2004 3.5 or a 2007 4.0

I would really like to use the 4.0, I know it's good , car was hit from behind at 70,000 miles 3 months ago. The other engine has a guarantee, but no info. I could install it only to find its old or even bad.

the plenum is different, but the mounts look the same. I can take the whole engine ,including the pcm and wiring harness, but would prefer to chop all the wires and hoses for a quick pull.

will it bolt up to my transmission? Are the mounts in the same place ? Can I use my pcm and harness with the 4.0?

if I have to go through the process of putting in a motor anyway, might as well get a little more displacement. The posted tourque and HP is the same as the 3.5 if I remember right, but I think with a pcm flash I should be able to get a lot more power than that.

So, what's different between 2006 and 2007 engines?

alternative
I could strip it to the long block and put all the 3.5 accessories on it.

both touring models

 

still lookingfor input. Do I have to havethe pcu reflashed for the 4.0? Can I use the 4.0 vehicle 's pcu as is?

I'v finally finished hand polishing the rod journals, there were 2 scratches with raised sides, if anyone tries using automotive body black sandpaper, expect to polish forever. I got some emery cloth, 180 and 320, 50 passes with the 180 knocked it back down to spec, and 320 has it nice and smooth.

Many people are over polishing their cranks. (Lol ), shouldn't go more than 400-600, because the tiny tiny scratches actually help hold oil. 2000 grit mirror polish is useless and counter productive. If the nice shiny crank journal actually TOUCHES the bearing, your engine is toast anyway.

want to argue that?

then why aren't rod bearings even shiny?

putting everything back together tomorrow, rebuilding a 4.0 properly, hopefully it last til that's ready. Got a rebuilt rod & piston, but I'm going to try to reuse mine first. (Have more bearings)

 

I am no expert in this matter,but I dont think the 4.0 will work in the place of the 3.5. The 4.0 uses the 62te and putting the Pcm from the 07 in your 06 will not work unless you use the 62te transmission and the wiring harness also the shifter on the 07 will be an autostick with 6 gears indicating on the gauge cluster so that leads me to believe that the inside wiring and or bcm will be different as well.
If someone can do a custom tune on your pcm to change the engine parameters and settings then I would guess it would work.
Are you using the 4.0?

 

Short answer, no. Long answer, yes, with some major upgrades to hardware and software. The 4.0L uses a different subframe (barely noticeable to the naked eye) and different engine mounts. Your 4 speed 41TE is completely incompatible with the 4.0l, as the 4.0l uses the 6 speed 62TE. Exhaust system isn't quite the same, and computer programming is different, meaning the ECM needs to be programmed for a 4.0l, which would mean a new and programmed ECM with the VIN from a 4.0l Pacifica would need to be purchased. The half-shafts are also different with the 4.0l. Also, when the Pacifica was updated for the 2007 model year, the Allpar website cited a new engine cooling system (being the radiator), as well as newer, more robust wheel bearings.

Hope this helps!