jaysett Posted August 30, 2014 Share Posted August 30, 2014 Hello all I'm sure it has been talked about but I can't seem to find it. I have an 88 Comanche with a 2.5L engine with a 4 speed trans, and the engine is tired. So I was told if I get a 4.0L engine and the 5 speed out of a 87 thru 90 Comanche or cherokee then I can just bolt it in with out changing the harness or anything else. Is this the case or is there more to it? Any help would be greatly appreciated. Thanks Link to comment Share on other sites More sharing options...
Jeep Driver Posted August 30, 2014 Share Posted August 30, 2014 That is not the case. Harness, ECU, fuel pump, ICM..........rad support and radiator......exhaust.......drive shaft.........and probably something else I can't think of at the moment. In short you are going from Renix TBI to Chrysler MPI.......ain't nothin' the same. Link to comment Share on other sites More sharing options...
Pete M Posted August 30, 2014 Share Posted August 30, 2014 just to add in another idea, easier than all that is upgrading the gearing with a 4.10 geared axle from the junkyard. :thumbsup: Link to comment Share on other sites More sharing options...
Eagle Posted August 31, 2014 Share Posted August 31, 2014 In short you are going from Renix TBI to Chrysler MPI.......ain't nothin' the same. No, he specifically said '87 - '90 4.0L, so he would be going from a Renix 2.5L to a Renix 4.0L. The engine room harness and ECU would have to be swapped, but that's not impossible. One of the guys in NAXJA-NAC (North Atlantic Chapter) did a complete 2.5L to 4.0L swap in one weekend. He said he worked his [bleep] off, but he did it in one weekend. Link to comment Share on other sites More sharing options...
onlyinajeep726 Posted August 31, 2014 Share Posted August 31, 2014 One weekend?! He must have not slept the entire weekend haha. Link to comment Share on other sites More sharing options...
Eagle Posted August 31, 2014 Share Posted August 31, 2014 One weekend?! He must have not slept the entire weekend haha. He pretty much didn't. He had to get it finished in time to drive it to school, and the 2.5L blew when he had less than a week left. The amazing thing is that he did a very good job of it -- no hack work, no butchery. Link to comment Share on other sites More sharing options...
jaysett Posted September 1, 2014 Author Share Posted September 1, 2014 Ok so there is no easy swap huh. That sucks. Any other suggestions. Or is the best solution to change the harness and the ecm with the engine. Link to comment Share on other sites More sharing options...
Pete M Posted September 1, 2014 Share Posted September 1, 2014 gear swap (axle swap, really). it's an instant kick in the pants. the 4spd 2.5s were undergeared from the factory with a 3.55 ratio Link to comment Share on other sites More sharing options...
JeepcoMJ Posted September 1, 2014 Share Posted September 1, 2014 I did a renix to H.O. conversion less swapping the fuel sender in 2 days. Renix 2.5 to Renix 4.0 with an 87-90 is about as easy as a motor swap gets. I do not understand how it is hard, or impressive, to do it. All the bolt holes are there. Get these parts from a cherokee. Engine (fully dressed) downpipe to crossmember Engine bay harness (unplug at firewall) and underdash engine computer and tcm as well radiator with lower positioning rubbers and uppers rad hoses frame side motor mounts coolant reservoir and hoses transmission transfercase with shift linkages spare rear driveshaft made to proper length trans crossmember and mount new fuel pump for 4.0 to put on your sender and swap it all. the 87-90 2.5's use a 4.0 core support with an adapter to put the 2.5 radiaor in. switching to and from manual will require other parts as well. Link to comment Share on other sites More sharing options...
Eagle Posted September 1, 2014 Share Posted September 1, 2014 I did a renix to H.O. conversion less swapping the fuel sender in 2 days. Renix 2.5 to Renix 4.0 with an 87-90 is about as easy as a motor swap gets. I do not understand how it is hard, or impressive, to do it. All the bolt holes are there. Get these parts from a cherokee. Engine (fully dressed) downpipe to crossmember Engine bay harness (unplug at firewall) and underdash engine computer and tcm as well radiator with lower positioning rubbers and uppers rad hoses frame side motor mounts coolant reservoir and hoses transmission transfercase with shift linkages spare rear driveshaft made to proper length trans crossmember and mount new fuel pump for 4.0 to put on your sender and swap it all. the 87-90 2.5's use a 4.0 core support with an adapter to put the 2.5 radiaor in. switching to and from manual will require other parts as well. I agree it's as easy as any swap could be. I still think getting it done in one weekend is impressive, but JeepcoMJ is correct -- it's pretty much a bolt-in swap all the way. After all, the vehicle was designed to take both engines -- how hard could it be? Link to comment Share on other sites More sharing options...
onlyinajeep726 Posted September 1, 2014 Share Posted September 1, 2014 I agree it's as easy as any swap could be. I still think getting it done in one weekend is impressive, but JeepcoMJ is correct -- it's pretty much a bolt-in swap all the way. After all, the vehicle was designed to take both engines -- how hard could it be? Unless it's an '86 haha. Then it's hack, weld, and BFH affair. :rotf: Link to comment Share on other sites More sharing options...
JeepcoMJ Posted September 1, 2014 Share Posted September 1, 2014 86 are the only years I wouldn't bother with a 4.0. If I have to fabricate stuff, I'm putting a bigger/better motor in. Link to comment Share on other sites More sharing options...
JeepcoMJ Posted September 1, 2014 Share Posted September 1, 2014 I did a renix to H.O. conversion less swapping the fuel sender in 2 days. Renix 2.5 to Renix 4.0 with an 87-90 is about as easy as a motor swap gets. I do not understand how it is hard, or impressive, to do it. All the bolt holes are there. Get these parts from a cherokee. Engine (fully dressed) downpipe to crossmember Engine bay harness (unplug at firewall) and underdash engine computer and tcm as well radiator with lower positioning rubbers and uppers rad hoses frame side motor mounts coolant reservoir and hoses transmission transfercase with shift linkages spare rear driveshaft made to proper length trans crossmember and mount new fuel pump for 4.0 to put on your sender and swap it all. the 87-90 2.5's use a 4.0 core support with an adapter to put the 2.5 radiaor in. switching to and from manual will require other parts as well. I agree it's as easy as any swap could be. I still think getting it done in one weekend is impressive, but JeepcoMJ is correct -- it's pretty much a bolt-in swap all the way. After all, the vehicle was designed to take both engines -- how hard could it be? I'm probably a bit spoiled with what I have bought for tools, and what I grew up with. Being properly equipped always helps. Link to comment Share on other sites More sharing options...
Eagle Posted September 1, 2014 Share Posted September 1, 2014 I agree it's as easy as any swap could be. I still think getting it done in one weekend is impressive, but JeepcoMJ is correct -- it's pretty much a bolt-in swap all the way. After all, the vehicle was designed to take both engines -- how hard could it be? Unless it's an '86 haha. Then it's hack, weld, and BFH affair. :rotf: True ... but the OP specifically said he has an '88 and was looking at '87 thru '90 engines. Direct fit. Link to comment Share on other sites More sharing options...
jaysett Posted September 1, 2014 Author Share Posted September 1, 2014 Thank you so much I really appreciate all of the help. Sounds like the renix 4.0 swap is the way to go. Thx for the list jeepcomj that's what I needed to know. Also is there any other specific markers on the renix 4.0 cherokee other than the year and the H.O badges? Also I think I have 4:10 gearing. Should I change it to, and if so, what ratio? Link to comment Share on other sites More sharing options...
Eagle Posted September 2, 2014 Share Posted September 2, 2014 Thank you so much I really appreciate all of the help. Sounds like the renix 4.0 swap is the way to go. Thx for the list jeepcomj that's what I needed to know. Also is there any other specific markers on the renix 4.0 cherokee other than the year and the H.O badges? Also I think I have 4:10 gearing. Should I change it to, and if so, what ratio? A Renix will NOT have "HO" badges. The HO came out in 1991, when Chrysler changed to their in-house injection/ignition system. Link to comment Share on other sites More sharing options...
JeepcoMJ Posted September 2, 2014 Share Posted September 2, 2014 What trans do you have right now? I will tell you that the "4 cyl = 4.10" concept is flat out wrong. You *should* have 4.10 gears IF you have a 5 speed. But if you have a 4 speed, you WILL have 3.55 gears. Just don't count on having 4.10's if you have a 5 speed, as it was still optional. Also, if you do have 4.10's, I would keep the gears, put in a 4.0/ax15 5 speed/np231, and a 3" lift with 31x10.50 tires. The 4.10's would be perfect Link to comment Share on other sites More sharing options...
onlyinajeep726 Posted September 2, 2014 Share Posted September 2, 2014 86 are the only years I wouldn't bother with a 4.0. If I have to fabricate stuff, I'm putting a bigger/better motor in. If I ever decided to do it again, I would likely have went a different route. I chose to do that because, 1.) it's what I had to work with for free, and 2.) as someone above pointed out, it is a fairly easy swap as it's all Jeep stuff to begin with. Being my first major overhaul, I wanted a fairly easy swap so I could learn a great deal of knowledge. I agree it's as easy as any swap could be. I still think getting it done in one weekend is impressive, but JeepcoMJ is correct -- it's pretty much a bolt-in swap all the way. After all, the vehicle was designed to take both engines -- how hard could it be? Unless it's an '86 haha. Then it's hack, weld, and BFH affair. :rotf: True ... but the OP specifically said he has an '88 and was looking at '87 thru '90 engines. Direct fit. Yes, I'm aware... I was just trying to be a little humorous while relating to the topic since I did the same swap, plus the additional fab work. Link to comment Share on other sites More sharing options...
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