Transmission: If you already have a manual transmission, you're in luck – the AX-15 transmission (common in many 4.0L Wranglers) is likely compatible. You might need to adapt some components or use a different clutch, but a complete transmission swap shouldn't be necessary. You'll definitely want to check the condition of your existing AX-15. If it's worn, it might be best to replace it while you're doing the engine swap.
Other Considerations:
* Engine Mounts: The 4.0L engine's mounts are different, so you'll need new engine mounts designed for the 4.0L in a YJ (1994 Wrangler).
* Wiring Harness: You'll likely need a wiring harness from a 4.0L Jeep Wrangler. This is a complex part of the swap. You may need to splice wires and adapt it to your existing system.
* Computer (ECU): The 4.0L engine has its own computer module (ECU). You'll need the correct one for the year and model of the 4.0L engine you are using.
* Exhaust System: The exhaust system will need to be modified or replaced to fit the 4.0L engine.
* Cooling System: Potentially different hoses and radiator may be needed.
* Driveshafts: The length may or may not need modification, depending on the engine and transmission used.
Complexity: This is not a beginner project. It requires significant mechanical skill, specialized tools, and a good understanding of automotive electrical systems. Many people find it easier to have a professional mechanic complete this swap, although it will be costly.
In short: While the swap *is* feasible, it's a major undertaking. Thorough research, a detailed parts list, and potentially professional help are highly recommended. Expect to spend considerable time and money.
