4.0 swap in for 4.2

[mike dumar]

Looking to swap out the tired 4.2 from my 90 YJ with a 4.0 I got a good deal on from a 92 YJ. I have both the wiring harnesses (dash/engine) but wondering what else I am going to need. Current Jeep is an auto with NP231 t-case. I have a fuel tank/pump from a 94 that I can use.

[mike dumar]

I guess a more direct question would be what do you do about the throttle cable to the transmission and the added various sensors. Also, the spedo is mechanical in the 90- and electric in the 92. Can I still use the mechanical one or do I need to convert something to adapt to the electric? Can I still use the 90 bellhousing or am I going to have to swap it out?

[resqme]

So I'm assuming you are mating to an automatic? I think you will have to figure out a way to adapt the TV cable unless you are replacing the trani as well as the AW4 in your YJ is primarily mechanical and the 32RH in the '92 was all electronic and the kickdown was handled by the computer.

You will also need:

- 4.0 manual trans computer
- vehicle speed sensor (stack one from Jags that run (www.jagsthatrun.com) on your mechanical speedo output on the t-case...retain your mechanical speedo
- high pressure fuel pump
- crank position sensor (you can use one from Hesco (http://www.hesco.biz/index.html) that mounts on the vibe dampener instead of replacing your bellhousing)

Probably some other stuff I can't remember right now.

[mike dumar]

Yeah, sorry it is an automatic. What's the reason why I need the manual trans computer? Is it because the 90 is primarily mechanical?

[resqme]

Yes, that's correct. If you use the auto trans computer it will be trying to give commands to the trani and looking for feedback.