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HELP!!! I have an 86 l/b, putting in 4.0 out of 87. Will a aw4 w/ np231 work? and what drive shaft will need? And to confirm will i need to mod the firewall? I think i might have got in over my head.

Any help would b awesome thanks

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You will need a radiator (and supports) from an '87 or newer 4.0L XJ or MJ. You will have to decide whether you want the '87 - '90 "closed" system type, or the '90 + "open" system type. If you are taking the electrics from the '87 donor vehicle, it will be set up with the thermal switch for the auxiliary fan in the left radiator tank. Most of the "open" type radiators don't have a place for this, so you're probably going to need the early style radiator.

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Leave the drive shaft worry for the very end.....You can do the entire swap and drive around in front wheel drive if you have to move it.....before you need to think about a drive shaft.

 

And IMHO go with the newer open system for cooling.... :thumbsup:

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A closed cooling system is one where everything is completely sealed. In the Jeep setup, the main coolant "reservoir" is a bottle that permits some expansion of the coolant. The advantages are that the coolant is less likely to get contaminated from outside sources, and that the boiling point of the fluid is higher (due to the greater pressures) so overheating and cavitation are less likely. Also, in the Jeep, there's constant flow of coolant through the expansion bottle, which leads to less crud building up, and added fluids get mixed in much more quickly. The disadvantages are that if you develop a leak, the greater pressure will make it become worse more quickly, and that the greater pressure will add heat to the cooling system.

 

An open system is not under much pressure. The main coolant reservoir is an "overflow" bottle... When the heat expands the coolant, it pushes out into the bottle, and any pressure is vented through the overflow tank. The lack of pressure means that cooling is more effective and leaks are less likely to develop. Heating to the point of cavitation is less likely. Because coolant travels back and forth from the overflow tank in small quantities and the overflow tank's vent is usually mostly just a hole, contamination can happen. The minimal coolant flow through the tank can also lead to crud building up in it, which could plug the overflow, which causes problems. Also, anything you add to the overflow tank may take some time to mix in. You can add it directly to the radiator, but in a full system, popping the rad cap will likely spill some coolant.

 

Jeep went from closed to open cooling in the XJ/MJ in '91, along with the rest of Chrysler's engine control changes that we call the HO. If you do deep water crossing or travel through extremely dusty areas (worse than just dirt roads) then a closed system may be better to keep out contaminants and/or keep your coolant from polluting the watershed. In all other cases, though, the better cooling ability of an open system will be better for you. If you'll be buying new cooling parts, I'd definitely recommend going the open route. If you've got a complete donor with a closed system sitting there, there's not all that much reason for you not to use it, just bear in mind I've seen lots of people convert their closed systems to open, but I've never seen anyone go the other route.

 

In order for your '93 AW4 to play nice, you'll need the transmission wiring harness and computer that came with it. If you've got them from the '87, it won't work properly. In the mean time, though, leaving the trans fuse out or the tranny computer unplugged will allow manual shifting, but will disallow second gear.

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I'm a rookie, i do not know about open and colsed system.

Any help

 

Easiest way I have of finding out from someone is ask....."what color is your rad cap"......if they say "what rad cap".....CLOSED......any other answer...OPEN.... :thumbsup:

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Thanks to everyone who has responded to the questions. Apparently i misunderstood what this section "mj tech" was for. The thread is very helpful but wouldnt have found it.

I'm not a mechanic, and want to save money on trying to do it myself. And be able to take pride in doing it. I will be getting help on the Facebook comanche group from now on. Thks again for those who chose to be positive.

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If you're polite and work with them instead of being defensive then Hornbrod and Cruiser will become your best friends. Cruiser has helped me with numerous problems on my truck for months and still gladly answers questions without telling me to eff off (quite amazed, honestly). Hornbrod has also been quite a good chap with a few situations. Most of us on here are men... we use tough love and bust each others balls. And yes I know this reply did not help the OP's problem at all. Just had to chime in since he said Hornbrod wasn't friendly. Good day fellas :D

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mj86,I believe you missunderstood  Hornbrod,The link was ment to help.I'll guarentee you your at the right site,This is the best and most helpfull group of guys on the internet for Comanche help.Search around the forums for what you need to know,If you can't find it searching,don't be afraid to ask,You will get the answer here,I've ask dozens of Comanche questions and every one of them has been answered,And answered quickly and in great detail.You will learn more about your truck here than anywhere else on the net.Guarenteed

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There is no right answer. Do some research and read the link. There are several different ways to swap a 4 0 into a 86. You can decide which way is best. Don just gave you one of them. With your entitled attitude you are better off with facebook teaching you the right way.

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MJ86, 

 

You really have found the very best Comanche resource on the internet right here.  The members here have done just about everything you want to imagine with and to their Comanche truck.  Sometimes, they have done the same thing several times just to make small improvements and the neat thing is that they will share that knowledge with you by answering questions, offering links, providing part resources and just about anything else, including some really good deals.

 

I am on my ninth year here in the Comanche Club and I still learn new things all the time.  You can improve your own knowledge by reading some of the build threads on this site.  There are likely more than a dozen build threads related to putting the 4.0 in an 86.  There are also other options, like upgrading the 2.8 V6 to a 3.4 V6 with fuel injection.  Again, a number of threads with a bunch of details and links that can help with that direction.  Our trucks are getting older and parts sources are drying up.  You will find alternate parts sources here also.

 

So stick around and you can get that 86 running great.

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Hornbrod thanks again for the link, I'm sure it will help me greatly. I came to this site to find y'all that have been there. I thought asking u guys was doing my homework. Ive read and talked to SO many people on this conversion, i have almost given up. But I love my Manche.

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