Bottom line: what will still function (or not) after an engine swap?

Howdy folks - new 08 JKU owner here. Not new to hot rods or fabrication but I am new to Wranglers, just picked up a nice 08 JKU for the wife - nicely upgraded with ProRock 44/60 and 37s and armor, and I'va question...but not about this Jeep. We like the JKU platform a lot, and my rock crawler is a big and highly-modified Dodge Dakota 4-door on 40s, and I'm considering pulling the Mag360/46RH/Atlas4, D60 and 14b from the truck and putting it all under another JKU. I'm eyeballing a nice 2008 JKU with a damaged engine, and my question is what will still work after an engine swap?

Scenario: Running/driving 2008 JKU: if I pull the engine/trans/t-case/axles and replace them with something else, and I leave the original engine/tranny/t-case/axle wiring harnesses all in place but not connected to anything OE...connect the battery...what will still 'function'? Will "everything" else work? Will the dash gauges work, will the wipers work, will the HVAC blend doors hot/cold work, will the power windows work, will the wipers work?....and what will not work? I imagine the speedo will need some voodoo to make it still work, but what just won't?

Suspension swaps/lifts/steering etc are easy so no worries about all that part.

Another option I have is to find a gutted JKU and put my own driveline and old school wiring harness in it, which isn't as daunting to me at it may sound, and it might be simpler to do that than to try to bypass the computers and such to have functional wipers, turn signals, head/tail/turn signal lights, etc.

So what's the consensus. If someone is considering an engine swap (complete with it's own stand-alone engine harness - in my case a Holley Sniper), what will and will not work?

I ask this because I'm battling the Dakota's remaining nanny computers trying to find ways to get some of the OE electronics to work. The engine/tranny/t-case all function nominally via stand-alone command and control (Sniper EFI/Ignition and 46RH tranny - no OE computers) and I fabbed a stand-alone dash with all functional (non-OE) gauges and indicator, and it wheels like a beast, but it's no-where near 'done', and while the HVAC and windows work I don't think the lights and wipers will...and I'm considering a smaller/lighter vehicle anyway and a JKU is a natural choice...but I want the Dakota's proven driveline under it, so, here I am.

I tried to find this general info in the multitude of stickies but alas I couldn't find it - pls direct me towards a thread or other location if this has been answered elsewhere, and thanks in advance.

Thanks for the insight and feedback.

Pics just for fun









- Sam

 

Welcome to JKF. Friendly group here, several have done LS swaps on Wranglers.. Be aware of state emission regs; Ian on FourWheeler did a show with an engine swap and he cautions about state regulations.

 

I can only comment here based on my experience with installing a Chev LT engine so all comments may not be quite correct. I had the JK ECU, The Chev ECU, the Chev Tranny T87 ECU and an interface computer. If you leave the Jeep computer in there most items not related to the engine will function, some you may have to turn off in the JK program and some will not work at all. Cruise control may not work, AC might but won't have the increase ide when on most likely. I would stay on the JK side for AC control. Dakota engine is old style computer so you need a start signal to the starter and a switched ignition from the JK side. JK fuel pump puts out 50psi so should be ok for the Dakota FI rail pressure. Then leave the Dakota ECU in there to run the engine and transmission. Good idea to go Dakota drivetrain. You might have to put it in and start the process of getting items running one by one. I used a Motech kit so off the bat most things worked but had an issue on three things. I can say you will need to have access to a proper scanning system to get codes turned on and or off and to scan while driving to troubleshoot. Checking thrown codes in this scenario does not help that much as you need deeper visibility into the JK side and the Dakota side. Not sure what works on the Dakota side though.
Dash gets it signals from the Jeep ECU. All wires go to that unit no cables. Speedo may work if you leave the 4 wheel sensors connected. Lots and lots of things to consider. When you remove the engine carefully label all wires that are disconnected even grounds as they are important. You have lots of work to do to figure this all out. Hope this helps.

 

great info thanks! The Dak's engine is stand-alone as well - it has a Sniper EFI and the trans enjoys computer-less C2. No tone rings etc in the axles, mechanical speedo cable - all very basic. Sounds like I would be looking at gutting the Jeep and installing my own wiring harness to control the lights, wipers, etc, run a Summit heater box with pull toggles to get heat/cold etc...

 

Do a Hemi swap. Everything will work. 5.7L with a 545RFE will bolt to your stock JK transferase. Did this last year in my driveway. Nothing to it. I got the bolt-in mounts from Jeep speed shop and harness and computer from Hot wire Auto. All plug and play, and only one computer. You'll need a 2008 Grand Cherokee computer, if you want to retain the OD OFF function. Have that reprogramed by Hot Wire Auto.

I think since I was able to reuse my stock drive shafts with the stock axels, there's a chance you may be able to retain yours also. The transmission going in almost the same location as before.

 

That is great info - thanks for that . We just got a decently built 08 JKU for the wife - and it has the 3.8, and she likes 'power', so we may take all of your info and apply it to her Jeep. Do you have a link to a thread for your buildup? - I'd like to check that out. Do you know which Ram(s) I would look for (year range, etc) - obviously 4wd and auto. Might keep an eye out for suitable donor trucks.

Meanwhile, thanks all the info folks - much appreciated

- Sam

 

Here's my build thread, only big thing I'm redoing right now is a Griffin radiator and a Camaro fan. Mine is also an '08, so for me I could have used any Hemi engine, car or truck, 5.7, 6.2. or 6.4. Install is a little different based on what you get. Best bet is a Grand Cherokee or a Commander. It already has everything you need, like the right timing chain cover and the exhaust manifolds. The transmission has to be a Ram 1500, 4x4, '06 to 2010. I went with the commander because it was the cheapest option. If money is not an issue than the 8 speed is the way to go. I had to get another trany to T case adopter, don't remember what ended up working, but that was another major pain.
Call and talk to Todd at Jeep Speed Shop and Chris at Hot Wire Auto.

Check out post #24 (I think). That has Todd's BOM for everything.

You don't have to have a kit, if you are a little creative, looks like you are!

If you go with a 5.7L, get a 2008 Grand Cherokee 5.7L ECU, got mine on ebay. Have Chris reprogram it and I also got the harness from him. Just get the bolt in mounts from Todd. Transmission mount is nothing but a flat plate that is drilled for the transmission mount and the stock JK cross member. Exhaust was the biggest pain, but it's also doable. There is a kit for that also, if you wanna drop another grand. I made my AC hoses, or that'll be another $500.
Unfortunately, I will be redoing the exhaust soon with a TJ fuel tank swap. I hate the JK tank.

Have fun!

https://www.jk-forum.com/forums/jk-g...2/#post4396127

 

Fantastic info - I replied to your thread too.

Thanks man,
- Sam