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Having a manual transmission will simplify the swap. Ive done research on my own, just to prepare for a hypothetical motor swap in the future. What I found (this is regarding a 2006 KJ and a donor vehicle of a 2006 Dodge Dakota also with a manual trans) is that the difference between the ECM's is minor. There are only about a dozen different pins on the connectors that are different. This is mainly due to the Dakota ECM running an engine with 2 more cylinders, and that the 4.7 has EGR whereas the 3.7 does not. The other major difference is that the Dakota's networking is all PCI bus. The KJ has a hybrid PCI and CAN bus setup. The ecm communicates with the body control module/junction module. It's basically your gateway module to all the other modules on the bus. Since the pinout is so similar and the modules are essentially physically identical I BELIEVE that the dakota ECM will communicate with the Jeep body control module. Where it will probably get tricky is with stuff like the immobilizer and ESP. The jeep's ABS module is CAN bus the Dakota is PCI. Again, the gateway/body control module in the Jeep provides the interface between the two bus types but to me, it's an unkown. Can you reflash the immobilizer or the ECM to a different VIN sequence, so that it'll start? That's something I don't know yet. I know that in certian vehicles, the VIN can only be written once, and the ECM and Immobilizer must be replaced together (talkin about older Mitsubishis). I'm not a chrysler tech and don't have that answer yet. I'm planning on taking on the module side of the swap sooner rather than later. The ECM for the Dakota is inexpensive enough for me to pick one up to play with. The first major hurdle for me is access to a factory scan tool - at the VW shop where I work, we DO have a Star Mobile scanner (chrysler factory scan tool) but only with software/license for the Routan (caravan) minivan. There's also a DRB III around there somewhere (for the older Sprinter vans), maybe I can get somewhere with that. I'll have to make friends with someone at the Dodge/Chrysler/Jeep dealer across the street... Other than knowing what the pinout of the ECM's is and the data bus types, I haven't personally verified anything. Once I actually make some progress I'll start a thread. I do know that Honduras got his 4.7 ecm reflashed and a custom wiring harness made, he said something about it over on KJ Country forum.
As far as motor swaps go I think it's actually pretty straight foward. I've seen a modern HEMI in a Plymouth Prowler... now THAT took some custom work. I Think that if you've got a gasser KJ the 4.7 makes the most sense by far for an engine swap, more so than building up the 3.7. I'm aware of hot cams for the motor that have about the same profile as what's in the 4.7 H.O, and there's a company (forget the name) that sells ported cylinder heads for the 3.7. If you do the labor yourself, 4.7 swap would be much less expensive. You're going to have to fabricate parts, change a bunch of other things, and deal with the inevitable parts breaking from the torque of a V8, but that's just the nature of hot-rodding. If it ain't broke, add horsepower 'till it is.
_________________ 2006 Sport 4X4, Deep Beryl Green, NSG370, NV241J, Lifted with OME 927/948 and Bilstein, JBA 4.5 UCA's, Custom 3" Rear Y-Link Extension and Swaybar Relocation, 265/75-16 Toyo Open Country AT2 tires, Black Plastidipped bumpers, flares, and doors, Pioneer speakers, Alpine head unit, 1200w Phoenix Gold Amp, 12" Dayton Reference sub.
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