This would be a terrible swap. More headaches and far less power then just doing a v8 swap

 

I have no need or want for a v8. And my old 4.0 was absolutely bulletproof. Again probably not doing it but curious

 

I saw it done once. The guy ran into MANY issues, and when it was all said and done he said it felt more gutless than the 3.8 it replaced. If you're swapping anything, go V8 or 8 speed behind the 3.6. V8 with 8 speed is chefs kiss

 

I saw it done once. The guy ran into MANY issues, and when it was all said and done he said it felt more gutless than the 3.8 it replaced.

Holy shit, you're telling me that a 480+ lb engine that's down 45 HP from the engine he swapped out feels gutless? I don't believe it! What a waste of time LOL.

 

Swap out the factory air box with a Mopar CAI...and it will sound just like your old 4.0...for a fraction of the cost and complexity.

 

A couple of pointless replies in here but some good info. Again, not going to do the swap, but I’ve owned two 3.6’s and two 4.0’s. The 4 liter was a better motor imo. I’m sure I will find an CJ or an XJ to restore and scratch the itch that way

 

i agree

 

The problem is even you you don’t have local emission testing it is against federal law to install and engine from
a earlier vehicle so it would not be legal for use on public roadways
Last time 4.0 jeep was made was 2006 so not legal on any JK as they are all 2007 and newer

 

Digger84 you took the words right off my keyboard..

 

“For light-duty vehicles, installation of a light-duty eng~ne into a different light-duty vehicle by any person would be considered tampering unless the resulting vehicle is identical (with regard to all emission related parts, engine design parameters, and engine calibrations) to a certified configuration of the same or newer model year as the vehicle chassis, or if there is a reasonable basis for knowing that emissions are not adversely affected as described in Memo 1A. The appropriate source for technical information regarding the certified configuration of a vehicle of a particular model year is the vehicle manufacturer.”
From

HTTPS://www.epa.gov/sites/default/files/documents/engswitch_0.pdf

 

I've been looking at the opposite. Possible future project....

Swap a 3.6 into an MJ. Less weight, more power, better transmission.

 

That would be a cool swap. I've only seen one person swap a pentastar into a non-penta platform

 

Better transmission?

 

Wa580 is an improvement over the aw4 and 42rle and tf999.

That is where the swap gets tricky. Wa580 needs lots of inputs

 

Seen AW4 last 400k in an XJ

 

The aw4 was a good transmission. The nag1 was considered a really good transmission as well until the 8 speed came and outshined it. The nag1 is rated at a higher torque input than the 8 speed though

 

A couple of these threads pop up in here often. "Can I swap a carbureted ford 302 into my jeep" etc.

Yea, you always can, but is it worth it to spend thousands installing an engine, transmission, and transfercase for little to no performance gain? An entire drivetrain swap comes with all sorts of additional costs.

People are swapping LS's, hemi's, and TDI's because someone has already figured it out and parts exist to make the swap quick, reliable, and relatively inexpensive.

 

that's why i didn't put the built carbureted 302 in my LJ nobody makes anything for that swap. people asked why would you want to put a ford 302 in a jeep duh because i owned a 302 it came out of my 83 ranger that got totaled when i young woman crossed the centerline and hit me head on thanks to her i have C5 and C6 fussed in my neck

 

Nag1 not for how long it may last, hardly. It is all about gear splits and lower first gear its OD gear is only .87. All older trans will have that .65+- Od that had to far a gap 4 speed autos. The 8 speed has even lower first then the Nag and that .65 OD. two overdrives

Its a rather well geared box. with tap shift. If it was behind they 3.8 or anything older it would make it feel like it had more power. Since its first gear is near a full ratio down. A 2011 down auto needed 4.88/5.13 gears to roll 35s. a 2012 UP can go with 4.1/4.56....all trans really. 3.6 would be much less responsive with a 42Le.

 

I don’t know all the transmissions by they’re model number as I haven’t had the sickness as long as some of you guys lol. But I will say I owned a 14 Grand Cherokee and initially loved the 8-speed auto as it made my Jeep super fast off the line. But that transmission was a nightmare; it was fussy skipped gears, got stuck between gears, needed software updates and when I traded the Cherokee in was needing a rebuild. I purposely only looked at jk’s as I don’t ever want that transmission again. If I were to get a JL I would have gotten a manual. I owned a lifted XJ years ago with the 4 speed auto and it was a bulletproof low maintenance trans…not as fast as the 8 speed but I don’t buy Jeeps to drag race lol.

 

The XJ was the AW4 a very very long lasting overdrive automatic transmission

 

I never should have sold the XJ. It was rust free and really clean. Traded it in on a truck in 2007, it was a ‘96…now would be worth 3 times what I got back then

 

There is nothing wrong with the NAG1 trans, and i don't know of any other Jeep trans before the NAG1 with the nice gear ratios we have in that one. Nag1 was rated at 428 ft/lbs torque limit so it's more than plenty for the JK at least in NA trim

Mercedes NAG1 / WA580 / W5A580 automatic transmission

Mercedes NAG1 / WA580 / W5A580 automatic transmission by Michael Dickens The NAG1 (WA580 or W5A580) automatic transmission found in many Chrysler products is an electronically controlled 5-speed transmission system with a lock-up clutch in the torque converter. The fifth gear is designed to...

www.allpar.com

The ZF 8 speed is faster and has even better gear ratios. There are different variants, i think the one is the WK2's v6 was the 8HP45 or 50, some need software updates but once is updated should be fine though i agree they could be more prone to issues because they're more complex, but they will wishstand more power, watch the 8HP90 or 95. 740 ft/lbs, the wk2 v8 used the 70 version.

https://en.wikipedia.org/wiki/ZF_8HP_transmission

So going with something less than a NAG1 or 3.6L in a 12+ JK is in my opinion a downgrade.
Simple stats on the proposed engine vs the Pentastar

4.0
190 HP at 4600 rpm
235 ft/lbs at 3200rpm
13mpg city /17 mog hwy

3.6
285hp at 6400rpm
260 ft/lbs 4800rm
17 city 19 hwy

stats on the trans
somebody mentioned 42LE compared to the NAG so check how inferior those ratios are in comparison to the NAG1 (wa580 below) and how the ZF8 has much better gear ratios

Trans/Gear	42RLE	WA580e	850RE
1​	2.84​	3.59​	4.71​
2​	1.57​	2.19​	3.13​
3​	1​	1.41​	2.1​
4​	0.69​	1​	1.67​
5​		0.83​	1.28​
6​			1​
7​			0.84​
8​			0.67​

The Manual JL's are plagued by a lot of clutch issues, among other issues, so unless you're thiking to add another $1500-2000 to run a better clutch, i wouldn't touch a manual JL with a long stick