4.7L PowerTech V8 Engine SwapEdit
Note: All of this info applies to 2.4L and 3.7L gas Libertys. I just can't see someone with a CRD wanting to replace their engine. The CRD has completely different engine mount brackets but does already have the correct transmission (at least in my case - MY 2005). The 2006 CRD uses a PCI TCM rather than the 2006 gas's CAN TCM, which could make swapping in a 2006 Dodge Ram CAN TCM more difficult. The CRD BCM is different from the Gas BCM and will probably expect the TCM to be on the PCI bus. In order to use the CAN TCM in the 2006 CRD you'd probably also need to swap out the CRD BCM for a gas BCM.
It was mentioned here that you need to get the same year engine for the swap to be smog legal. Dont worry about that. They are all illegal swaps. This is only legal in places with no emissions testing or on jeeps that will be used strictly off road never on a public street or highway.
In order for the engine to be compatible with your factory emissions equipment you'll need to make sure you get the same type of PCM (Powertrain Control Module) as you originally had. There are two types of PCMs: JTEC and NGC. JTEC is the older controller and NGC is the newer controller. There's an easy way to tell the two apart: an NGC PCM has four connectors on it because it integrates the TCM (Transmission Control Module), while the JTEC has three connectors on it because it uses a separate TCM. If you have Sentry Key you'll need to have your VIN number programmed into the new PCM in order to start the Jeep. Simply reprogramming the VIN will create an unerasable DTC, the only way to prevent this DTC is to have the PCM properly reprogrammed using a DRB III so its secret key matches the secret key in your SKIM (Sentry Key Immobilizer Module). You'll want to grab the original PCM and wiring harness when you pick up the engine or you'll be stuck trying to match one later on.
Note: The 2006 Libertys uses a hybrid bus system where the PCM (engine), gas TCM (transmission), and ABM (ABS and ESP) all use the CAN Bus and everything else uses the PCI Bus. The BCM (Body Control Module) acts as a bridge between the PCI Bus and CAN Bus. The 2006 Dodge Ram PCM and TCM also uses CAN, so you might be in luck here.
Not that I've done any actual measurements (I can't find any online) but the 4.7L PowerTech V8 is probably the only easily swappable engine that will fit. This engine can be found in the Dodge Dakota, Dodge Durango, Dodge Ram, Jeep Commander and Jeep Grand Cherokee. In my model year, 2005, all of these vehicles except the Dodge RAM utilize the CAN Bus rather than the Liberty's PCI Bus. This means that for the PCM to be electrically compatible with the rest of the Control Modules in my Jeep I have to use an engine out of a Dodge Ram.
All vehicles with the NGC PCM have an integrated TCM, which means that unless you find a way to reprogram it, you're pretty much stuck with the transmission that originally came with the engine. The 2005 Dodge Ram, the only vehicle with an engine compatible with my Liberty, has two transmission options: the 45RFE/545RFE and 48RE. As far as I know, the 48RE is only paired with the Cummins diesels. This leaves the 45RFE/545RFE as the only option. Luckily, the 545RFE should mount perfectly in the Liberty, as it is the same transmission that the Liberty CRD uses.
With the Liberty's relatively small grill and the larger engine, you'll need a more efficient radiator to dissipate all of the heat.
With the efficiency of modern cooling systems, the likelihood of upgrading the cooling system being required is fairly slim.
In theory width and height wise the 3.7L should be the same size as the 4.7L. Looking at the service manuals the mounting points on the sides of the two engines look identical. If the 3.7L motor mounts can support the weight of the 4.7L then you should be able to bolt them directly onto the 4.7L and directly into the engine cradle brackets. The 4.7L mounts in the 2002 Grand Cherokee appear to be the same as the 3.7L mounts in our Libertys. The 3.7L wet weight is 422 lbs while the 4.7L wet weight is 474 lbs, making for a weight difference of 52 lbs, which shouldn't pose a problem. Another issue is whether the brackets on the engine cradle can themselves support the weight of the 4.7L. Luckily, for obvious reasons, the added bulk of the 4.7L is forward of the old engine, so clearance in the firewall area shouldn't be an issue. The hardest part of this swap is definitely the motor mounts, if only because the dimensions and fit aren't known.