Can I replace my 1989 jeep Comanche 4.0 with a 1998 jeep Cherokee 4.0 and have all the electrical plug ins and motor mounts work without problems?


Asked by jeepmj Nov 10, 2012 at 07:41 AM about the 1989 Jeep Comanche

Question type: Maintenance & Repair

I need another 4.0 engine for my 1989 jeep Comanche.

2 Answers


-In theory, yes. I just replaced a '96 engine & tranny in my '88 Comanche. -There were no significant problems in changing the engine; the electronics were the hard part. -You will need the COMPLETE wiring harness from the donor engine. You don't say if you have a stick or auto, but if you have a stick and the donor is an auto it will be "easier" to get the donor auto tranny as well. Yes, that might mean a driveshaft change. Mine was a 5 speed & we had to go auto because the engine ECU wouldn't work with a stick tranny. -The MAJOR problem was in the fuel supply. The older fuel pump and return just wouldn't handle the higher pressure of the new fuel rails. The fuel tank from the donor Cherokee wouln't fit so I will freely admit that we screwed up somehow in trying to "Mickey Mouse" the connections. My fuel guage doesn't work; it pins out at either full or empty. -We did NOT change the differential gearing. If you go from stick to auto you might want to check that out. I got crummy gas mileage before the switch & still get crummy gas mileage. -Unless you have your heart set on another 4.0, and I'll admit that they are fantastic engines, you might want to check with Advance Adapters or some of the other Jeep engine swap companies. If I had it to over again I'd go with the Chevy/GMC 4.3 liter V-6 and a 700R4 transmission. I know Advance has all of the parts. -Whichever way you go, good luck!

2 out of 2 people think this is helpful.
Wade Scruton

so how much are you talking money wise to swap? i just bought a 87 comanche 4.0l 6Cyl auto and my last jeep a 02 grand cherokee laredo 4x4 automatic.i would like to swap the engines and was wondering if an older model like a 95-99 would be easier?

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