For the 97-06 Jeep Wrangler TJ/LJ Platform the most direct and simplest HEMI Conversion uses a GEN 3 HEMI out of a 06-08 Truck or SUV like the RAM or Durango. As noted, the TK Series HEMI has the alternator and AC compressor mounted high on the front of the engine. We try and utilize only 06-08 donor truck engines. We leave the MDS unplugged and convert the harness to a PCI communication platform.
Using a 2005 HEMI ECU which are PCI based, it will communicate with the factory cluster found in 2001-2006 TJ/LJs. This setup can also be easily be made into an emissions compliant build in any 2003-2006 TJ/LJ chassis or into a 97-02 chassis with adding the NVLD and PURGE Solenoid from a 03-06. We have done emissions compliant swaps with both swapping out 97-02 fuel tanks with 03-06 tanks as well as replumbing the 97-02 tanks. EXCEPT IN CALIFORNIA- in California, with their swap laws, you cant make an 06 Wrangler emissions compliant because by their law- it requires an 06 computer. The 06 HEMI computer and the Jeep cluster and NVLD systems are not compatible.
The GEN 4 5.7 HEMI can be used in the TJ/LJ swap but it comes with compromise. The GEN 4 cannot easily be made into an emissions compliant build. So if you have to meet emissions requirements- your pretty much locked into a GEN 3 HEMI. The GEN 4 engine must be run with a GEN 4 CANbus ECU or you will burn up the engine within a few minutes as there is no VCT or VVT control. The GEN 4 ECU as stated above is not compatible with the stock Jeep cluster so you have to run a full set of aftermarket gauges. With the increased HP and TQ in the GEN 4 HEMIs, the stock Jeep TJ/LJ chassis is subject to higher levels of flex from the torque twist.
The most common transmission used in the swap is the 545RFE 5 speed automatic transmission which was found in Chrysler/Dodge/Jeep vehicles from 2003 to 2011. In 2012 they went to the 645RFE and it is identified by a GREY transmission connector plug. The 645RFE can be used but the valve body should be swapped to the 2011 earlier version.
If swapping into a 2003-06 automatic equipped Jeep, the stock shifter will work with the 545RFE transmission.
If going into a 97-02 automatic equipped Jeep, you will have to swap the shifter assembly out for the stock 03-06 set up- floor plate, shifter and cable.
The HEMI can be backed up by a manual transmission for those who want to keep the fun pedal. Utilizing a conversion bellhousing and the JEEP NV3550 transmission found in the 2000-04. Stronger than its AX15 predecessor, the NV3550 can handle torque up to about 350 ft lbs.
We really don’t recommend any other manual transmissions in the TJ/LJ platform. You can of course mate the Getrag 238 to the HEMI but with its length, it kinda makes it more difficult to install and affects the overall driveline length.
The stock NP231 out of the automatics will bolt up to the 545RFE Transmission as the bolt pattern to the case is the same and the input gear splines is the same as well at 23 splines. These transfer cases have a ‘short input gear.’
If your transfer case has a ‘long input gear’ you will need to either do 1 of 3 things… the first is the recommended solution- take the case apart- which you are probably going to be doing anyways for a SYE kit- and swap in the “short” gear. Option 2- you can source a ½ spacer and put it between the trans and transfer case. You may need longer mounting studs with this set up. Option 3- you can cut off approx. ½” or so off your long input gear, chamfer the outer edges and check fit. Your Transfer Case must meet the transmission mating surface flush, with no resistance in this option. If it doesn’t mate flush you need to trim off a little more.
Transfer Cases found behind the NV3550 Manual transmission are 23 spline input, most commonly long input. If youre keeping the manual transmission than there’s nothing to do but bolt it back up during the build. IF you’re going from manual to automatic, then more than likely you’re going to have to choose from one of the 3 options above.
Transfer cases found behind manual transmission like the AX5 and apparently some AX15s have a 21 spline input gear and will not mate to the 545RFE. The 21 spline must be swapped out to a 23 spline input gear.