92 YJ 4 Cyl to a 6 Cyl
- Thread starter Jerry311
- Start date
You will need to replace the engine, transmission and the input shaft on the transfer case. I'm not sure about the rest. The trans in the 4 cylinders can't handle the torque/power of the 6. Transfer case on the 4 cylinder uses a 21 spline input shaft and an ax15 or nv3550 transmission (used with the 4.0) has a 23 spline.
I'd go nv3550. Its a better transmission than the ax15. You definitely want an external clutch slave. The internals on most yj's are nothing but problems.
In CA, you will also have to go to a smog referee. The motor must be 1992 or newer for your jeep.
jeff_in_rc
New member
Good info MarkW13 but I will add that he will also need the ECM and complete under hood wiring harness to match the engine to the jeep. Then you will need the 6 cylinder fuel pump and possibly the instrument cluster. A guy in our club did this years ago and when it was all said and done he said "should have bought a 6 cylinder jeep!"
I was going to make that suggestion. I converted a 4.2 to fuel injection. The cost wasn't nearly as expensive as an engine swap and I felt like it would have been better to buy a different jeep. The hard part is the emotional connection. I really liked that jeep despite it's thirst for cash.
I suggest enjoying the jeep as it sits.
Jerry311
New member
Yea I think I will just enjoy it as it is. Sounds like more trouble then its worth. I have a 350Hp Subaru if I feel the need to go fast. :crazyeyes:
I did the 4.0l swap a few years ago. The motor mount perches need to be cut off the frame and moved ahead. Trains swap, I used the nv3550. The dash and fuel pump do not need to be changed. The pcm send the tach signal to the dash. You do need the computer for the 4.0l and I would recommend the engine harness also. If you can't find the harness, you can open the harness and add the two injector harnesses that are missing. You will need to drill out the plug to install the wires. That's what I did because I couldn't find a decent harness when I was doing the swap. Some of the wires need to be moved also, iirc. Unless you are mechanically inclined, and enjoy wiring, don't bother. I had done everything else to my jeep, lift, arb's, custom bumpers and sliders yada yada yada. For me it was easier and quicker to do the engine swap. It took 2 1/2 days starting Friday nite after work. Running on the 4cylinder computer cuz I bought a bad 6cyl pcm. Had to wait till Monday to get a replacement.
BABOOZLE
Caught the Bug
I've spent hours and hours the last few months researching engine swaps. Everything from the 4.0 to 4.3/4.8 vortec, AMC 304 and 4BT. That also involves transmission, transfer case and sometimes even axle research to make sure everything works well together. Adapters also kill your pocket because they all seem to be $500. I finally decided to roll with what I have because my 2.5 is reliable and a good little engine. Once it breaks then I'll upgrade. Only cheap and easy way to do the engine swap is to have a donor vehicle. Upgrade your TB to the 4.0 TB and throw on an electric fan for noticeable gains you can feel and see. Then do an 8.8 swap in the rear. Good Luck.
I did the 4.0 swap in about a weekends time, a little at a time. I had the most issue with the trans and motor mounts not being the same. Wiring was easy cheesy! I just taped the two extra injector wire sets to the old loom, and then put the convoluted tube back over it. I kinda did the opposite of what most people would do, I shifted the motor, trans and tcase back almost an inch, ditched the tcase drop and cherokee z-bracket and slotted the trans skid to have a little adjustability. So I basically ended with everything back one inch, tcase dropped 3/4 inch, and skid plate in stock location.