87Chief Posted July 10, 2017 Share Posted July 10, 2017 I am in the middle of swapping my 4.0 into my 87 2.5 and need some help with the transmission wiring.. I acquire a 88 4.0 aw4 combo donor, got the engine wiring harness, computers (transmission too), pretty much stripped it down. I am wanting to go with an ax15 or nv3550, but I'm not sure I can use the current computer I have since it had a aw4 in it.. I don't want to replace the interior wiring, but I do have some loose wiring from the aw4 in my engine bay at the moment, can I get rid of those if I'm going 5 speed? I guess my question is do I need to get a 4.0 5 speed computer? Thanks Link to comment Share on other sites More sharing options...
Jeep Driver Posted July 10, 2017 Share Posted July 10, 2017 Your engine should run just fine without the aw4 wiring. But I don't see how you are going to get away without swapping the interior harness, 2.5 ECU is different from the 4.0. Link to comment Share on other sites More sharing options...
87Chief Posted July 10, 2017 Author Share Posted July 10, 2017 Yes, I know the ECU is different. I'm going to replace to the 2.5 ECU with a 4.0, I'm just not sure which one I could use, the auto or do I have to get a 5speed ECU? Link to comment Share on other sites More sharing options...
Jeep Driver Posted July 10, 2017 Share Posted July 10, 2017 Yes, I know the ECU is different. I'm going to replace to the 2.5 ECU with a 4.0, I'm just not sure which one I could use, the auto or do I have to get a 5speed ECU? I don't think it matters, guys unplug their TCU and the engines run fine. Link to comment Share on other sites More sharing options...
87Chief Posted July 10, 2017 Author Share Posted July 10, 2017 Ok, thanks for the replies! Link to comment Share on other sites More sharing options...
Minuit Posted July 10, 2017 Share Posted July 10, 2017 I think I remember reading that there are some minor differences in programming between the auto and manual ECUs, but it should work just fine. Link to comment Share on other sites More sharing options...
ParadiseMJ Posted July 11, 2017 Share Posted July 11, 2017 If it has the AW4 TPS, it only needs one side of it. Don't exactly know how it wires in but you shouldn't need to plug in the NSS side. The manual TPS is crazy expensive. I also don't exactly remember how , or why the manual would even need the TPS...or the TCU either, but my 5 speed DID have a TCU and a TPS (but only one side was used) in it when I ripped it all out and put in the AW4 harness. If you're replacing the ECU, see if you can get a 90 ECU from a Jeep with a 5 speed. It's 89 or 90 years that will give the engine a tad more HP...extra poop...since you're replacing it anyway. Click this: >>> http://comancheclub.com/topic/42705-more-power-form-renix-87-and-88/ Link to comment Share on other sites More sharing options...
87Chief Posted July 11, 2017 Author Share Posted July 11, 2017 Thanks! Link to comment Share on other sites More sharing options...
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