Question about 5.2 Magnum swap into 98 TJ


wickedjeeping

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Hey everyone how's everything going. I have a question, I've been looking but only come across newer tjs with magnums. I own a 98 tj with the 2.5 5 speed. I recently picked up a 98 gc with the 5.2. I'm going to be doing the swap soon and my question is about engine harness. Both jeeps are ccd. I'm going to be converting to an auto using the gc trans. Can I use the gc engine harness and ecm and just plug the tj dash harness into the ecm as well? I wont be changing anything on motor or trans going to be directly swapping them into tj. thanks
 

Wildman

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Hey everyone how's everything going. I have a question, I've been looking but only come across newer tjs with magnums. I own a 98 tj with the 2.5 5 speed. I recently picked up a 98 gc with the 5.2. I'm going to be doing the swap soon and my question is about engine harness. Both jeeps are ccd. I'm going to be converting to an auto using the gc trans. Can I use the gc engine harness and ecm and just plug the tj dash harness into the ecm as well? I wont be changing anything on motor or trans going to be directly swapping them into tj. thanks

There are more than one of us on here that have a Magnum V-8 in our TJ's.
If the TJ is 2003 or newer you can't legally swap a Magnum engine into it since they stopped offering the Magnum V-8 in 2002 except for some VERY rare 2003 trucks.
There is a little more to it than just swapping in the GC wiring harness and plugging the TJ plug into the PCM but it really isn't that hard. And using a GC engine & auto trans is the preferred engine/trans combo as the starter is on the passenger side in Jeep and on the drivers side on Dodge vehicles.

Look at my build thread for some help with the wiring plus a search for other threads on here.

You'll either need a different transfer case or change the input gear in your t-case. With the 4 cyl you have a 21 spline input but the 44RE in your GC has a 23 spline output shaft. The t-case in your GC might work but it might also be a full time t-case.
 
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wickedjeeping

wickedjeeping

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There are more than one of us on here that have a Magnum V-8 in our TJ's.
If the TJ is 2003 or newer you can't legally swap a Magnum engine into it since they stopped offering the Magnum V-8 in 2002 except for some VERY rare 2003 trucks.
There is a little more to it than just swapping in the GC wiring harness and plugging the TJ plug into the PCM but it really isn't that hard. And using a GC engine & auto trans is the preferred engine/trans combo as the starter is on the passenger side in Jeep and on the drivers side on Dodge vehicles.

Look at my build thread for some help with the wiring plus a search for other threads on here.

You'll either need a different transfer case or change the input gear in your t-case. With the 4 cyl you have a 21 spline input but the 44RE in your GC has a 23 spline output shaft. The t-case in your GC might work but it might also be a full time t-case.
the transfer case in the gc is full time. I was planning on chaning input shaft so I can swap the tjs over onto the gc. Both jeeps are a 98 so im not worried about the year. since they were the same year I was hoping the harness would be a lot easier. I keep reading and seeing newer year tjs and dodge 5.2s.
 

Wildman

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the transfer case in the gc is full time. I was planning on chaning input shaft so I can swap the tjs over onto the gc. Both jeeps are a 98 so im not worried about the year. since they were the same year I was hoping the harness would be a lot easier. I keep reading and seeing newer year tjs and dodge 5.2s.

You will need to blend the two wiring harnesses together. There are parts of the GC harness that you are going to have to remove as they aren't needed for the TJ. But it isn't really hard you just need get the wiring diagrams for the 98 GC & your TJ. You can find the factory service manual here on this site so you just need to source the GC FSM.

When you start looking for the input gear for your t-case make sure you have one for the later model t-case and also either get the extended seal or a long input gear or you stand a chance of having a leak.
 
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wickedjeeping

wickedjeeping

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You will need to blend the two wiring harnesses together. There are parts of the GC harness that you are going to have to remove as they aren't needed for the TJ. But it isn't really hard you just need get the wiring diagrams for the 98 GC & your TJ. You can find the factory service manual here on this site so you just need to source the GC FSM.

When you start looking for the input gear for your t-case make sure you have one for the later model t-case and also either get the extended seal or a long input gear or you stand a chance of having a leak.
do you know where on this site I can find the diagrams? what is the fsm? sorry for the questions and thank you for helping
 

Wildman

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FSM is factory service manual.


The thread is 199 pages but a lot of good information in it.

 
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wickedjeeping

wickedjeeping

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FSM is factory service manual.


The thread is 199 pages but a lot of good information in it.

thank you. I started to read and it seems like everyone is using dodge motors and ax15 trans so it makes it a little harder for me keeping it auto and trying to figure out wiring. if I have to is there someone I could outsource it to?
 

Wildman

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thank you. I started to read and it seems like everyone is using dodge motors and ax15 trans so it makes it a little harder for me keeping it auto and trying to figure out wiring. if I have to is there someone I could outsource it to?

There are people who did a auto swap also. It is a LONG thread but as I said some good information.

When you get to your exhaust if I remember correctly the GC manifolds won't work. The 92-93 Dakota manifolds are bigger and flow better if you are going to use stock manifolds.

Here are some cheat sheet notes I saved from a few different people who did the swap. Once you start looking at the diagrams you'll start seeing that there are many similarities between the two.

Read this thread, Rick did the V-8 swap and used the GC wiring harness.


Here is another thread on this swap.


 

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