Manual vs. Automatic ECU for 4.2 to 4.0 swap

R

rgirardi

Member
Joined
Mar 17, 2021
Messages
37
Location
Raymond NH
Hi
I am going to swap in a 1995 4.0L into a 4.2 L 1988 YJ, I have found several engines/harnesses/ECUs but they are all out of an automatic Jeep. In the early years will the ECU from an automatic tranny work with a standard. I believe the engine Managment system was very simple so the type of tranny shouldn't matter. Just wanted to see if I am wrong. Thanks Ralph
 
You can use any 91-95 4.0 PCM on a manual 4.0. The only picky combo is a 94-95 automatic. Those need the 94-95 PCM for their locking torque converter. Their TC will burn up if the PCM is not locking it up in 3rd.

You can not use any 2.5L PCMs to run any 4.0 drivetrain.
 
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