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2004 gtp swap everything into 99 gt

L

lance4682

New member
found a 2004 gtp with 100,000 miles on engine and tranny .i am taking the seats that seems easy enough but what am i getting myself into trying to swap the engine and tranny into my 99 gt. i am not a mechanic but my brother in law is so you can be specific as possible. any advice what to look for links to the subject would be appreciated as swap and gtp as keywords into the search engine seem to be to broad of terms....thanks
 


The swap will not be easy in the least.

We are talking completely different wire harness, different and wrong transmission that could work with an older car/pcm. You'd need a GTP pcm from 99-02 (an 03 might work), wire harness from a 99-03 GTP, tb plate adapter because 04+ is drive by wire and 97-03 is cable TB. I'm sure many other odds and ends and a custom computer tune to make it run.
 
so i could go to the junkyard get a wire harness and pcm from a 99 -03 gtp....where would i be able to find a throttle body adapter,and would a canned tune from someone like intense,overkill,etc be sufficient.
 
lance4682 said:
so i could go to the junkyard get a wire harness and pcm from a 99 -03 gtp....where would i be able to find a throttle body adapter,and would a canned tune from someone like intense,overkill,etc be sufficient.
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A junkyard can get you a PCM.

Vendors sell TB plates.

The transmission will not work without removing some parts and replacing them with older parts. The 04+ is controlled different and has parts that only going to on the 04+ computer. It's almost easier to just get a 99-02 transmission (03 is different again and requires more changing of various items).

l67ss said:
Why would he need the harness?
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I think big picture, for direct swaps with no addings of sensors/wires. Is it 100% needed, no but if can make it plug and plug sorta.
 


use the 99 gt trans and swap the motor over. You'll need a tb adapter, tb, fuel rail, and to extend some of your harness.
 
you can controll an 03+ trans with the earlier 97/98-02 pcm's with just moving a few pins and retaining your external range switch.

youll have to fart with the trans cooler lines if your radiator isnt a quick connect at the trans cooler
 
so the transmission is the difficult aspect of this swap. i ask because my gt trans has 170,000 on it and to be honest looks like the fluid has never been changed so i would like to get this tranny in it hoping that it will have more life in it...... as for the motor is it just drop it in and start sort of thing after i figure out the harness and pcm ?
 




Im not trying to be sarcastic but learning the wiring diagrams and how to use a multimeter could make this a whole lot easier than swapping a bunch of parts and cost a ton less. Besides if you have the entire 2004 car I'd use as much electronics as I could from the 04 so that that its mostly oem wiring, the rest is just body harness.
 
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