Questions about 2.5 to 4.0 engine swap

Rico Suave

Member
Original poster
Joined
Nov 15, 2020
Messages
29
Location
Kentucky
Ok, I have heard several different things- wanna ask the experts.
98 TJ 2.5 with 3 speed auto. If I drop in 4.0 what all do I have to replace?
 
Yeah I know I need motor mounts and slide the engine a few inches. I recently was told everything will bolt up and plug and play as long as I got a new computer
Haven't done it so I don't know, personally if I was spending the time I'd go LS before I'd go 4.0 if you can afford it.
 
Helped someone do this around 10 years ago. New motor mounts, PCM for 4.0 and harness from 4.0 pretty plug and play. Don't install the distributor off by one tooth like we did and wonder why it didn't run right ;). As a bonus you will have 4.10s and a 4.0. I was the harness guy and had FSM for 2.5 and 4.0 I recall doing some wiring work as we didn't get the whole 4.0 harness.
 
You need.
A transmission that will bolt up and hold up to the 4.0.

New trans mount

Cut and reweld motor mounts

Add two wires for the extra fuel injectors

Cut your fan shroud shorter

New ECU

A 4.0. duh.

Possibly a new front drive shaft

Possibly some brackets, power steering hoses, etc depending on how it all lines up.

New radiator hoses

Not to mention all sorts of fluids lubes, maintenance items,and odd and ends.