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  1. #1
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    Default 05 GTP swap into a 04 GT1 project... need some bcm/wiring gurus to chime in.

    OK guys I've been doing lots of research and have found lots of info on most of what I'm doing here but I need to weigh my options and decide on a game plan before I start swapping parts out... I drive a 04 GT1 with 261,000 miles on it. 3rd owner, origional engine and transmission, purrs like a kitten and shifts great but the electronics are starting to give me fits and well who wouldnt want more options? I scored a killer deal on a 05 GTP with no title or key as a parts car. It appears to be fully loaded to my knowledge. Same color interior, heated leather, dual climate, hud, monsoon, 5 button, 10 spoke 17s (my favorite wheels)... you get the idea. The car was running and driving when towed and only has 138k on the odometer so it should have plenty of life left on engine and trans, although I have not got around to getting it started since I don't have a key... to sum it up the poor owner lost his only key, got the car towed from a public parking lot, then couldn't afford the get it out of the tow yard and have it hauled to a dealer to have a new key made. So it was seized for storage and sold to me for $400!

    So here's my current situation. I see no need in swapping the engine or trans right now. I drive 100 miles a day so I want to squeeze all the life out of my engine/trans before I start running the clock up on the GTP engine/trans. And I want to take the time to save up for supporting mods to drop pulley size and do gaskets and general maintenence on everything. So for now I'm leaving that part alone.

    I've already swapped the leather seats and I'll be swapping the 17s Monday after I pick up a used tire to replace one of the bad ones. Went ahead and swapped the GTP grills and I'm going to grab the exhaust tips too and get rid of those heanous black gt tips.

    The HUD swap write up is simple enough as is the 5 button swap. The monsoon I could care less about. Already have a aftermarket head unit and system for the car that I need to install...

    That's the easy stuff. Here's where it gets complicated... one of the biggest issues with my car is the hvac system. When I got the car it had the common water leak through the cowl. Owner had already replaced the blower motor but it still has issues I'm assuming all started because of the water leak. I'm not sure really. I fixed the leak and got a new cabin filter. I replaced the resistor but still no blower motor. Eventually I took a volt meter to the wiring and found out there's no 12v or speed signal coming from the control panel. (This is the 3 button panel with the turn dial blend doors and fan speed) So finally I got tired of not having air and heat and wired the blower motor to the battery with a toggle switch ground. Worked great for ac. I just turned the fan on any speed so the ac kicks on then flip my blower switch and I have ice cold air. Then winter came and when I switched the temp knob to hot it stopped blowing. I also realized on hot or cold nothing blew from the floor or defrost vent. Only face vents and only cold air blew. So I took a closer look at the heater box and realized it was broke in half where it's plastic welded from the factory. I've rigged it back up to where I will blow hot or cold now and vent selection works but it still isn't blowing hard. So I need a heater box and I need a hvac control panel. I was about to buy both of those until I got this parts car. I'd rather not deal with a dual climate hvac swap after reading several post saying "it's impossible" but I'd also rather not buy that stuff when I have good parts in this parts car. Not to mention I'd like to get these heated seats working. So I'll need the hvac control from the GTP for the buttons.

    Basically I need some input from someone who knows what they are talking about or has experience with a swap like this. So since the heated seats and dual climate hvac rely on the bcm could I simply put the bcm out of the GTP into the gt? Will I also need to swap the whole harness in order to use the heated seats/hvac? And the most important thing to me is will swapping the bcm from a 05 into a 04 cause dtcs or security anti theft problems with my 04 ignition and 05 bcm? (Remember I have no key for the GTP so I can't swap the ignition.) My car has no check engine/abs/srs lights on currently and I want to keep it that way. And if I can swap the bcm is it possible to change the milage and vin stored inside it to match my car? I'm not against buying a tech2 if that's what it takes. Would it be simpler to reprogram my bcm to work with the heated seats and hvac?

    Lots of questions guys I know but if you've read all of this and can help me out thanks. I'll post some pics of the cars once I find somewhere to upload them so you can see my swappage as I go along. This will be my official project thread.

  2. #2
    Killa Bee Scottydoggs's Avatar
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    Default Re: 05 GTP swap into a 04 GT1 project... need some bcm/wiring gurus to chime in.

    forget about swapping anything inside the cars, like the bcm, dual cc and so on. wont work. hud is do able if you want, that moonson pos wont work at all, so f that pos. if the speakers are still good we got a few guys looking for them tho.

    drop both cars cradles with engine and tranny bolted to them, and swap them. you'll want to grab the 05 engine harness swap that, then use the pcm, the box in the air filter box.

    98 Buick Regal GS, F body brakes, Caddy STS wheels, tinted tails L36 bottom end, lightly ported heads, 1.95 roller rockers, headers, 3.0, FSIC, 42 lb injectors, a BrandonHall rebuilt trans, DHP tuned by me. https://goo.gl/gpV5kW

  3. #3
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    Default Re: 05 GTP swap into a 04 GT1 project... need some bcm/wiring gurus to chime in.

    Looks like I won't have any need for a bcm swap or reprogram anyway... I finally figured out my hvac control unit and got it working (that's the only real reason I needed to swap it)... and I rigged my heater box up from where the last jackass broke it in half for their "heater core install". Everything works now. As for the monsoon system I don't care much about using it... I already planned on using a aftermarket unit anyway. I don't know if the monsoon speakers are good or not honestly... never had the ignition on with the whole no key situation... but I have all 5 speakers and the head unit and amp so if anyone is interested pm me. I live in West KY or will ship to continental US. Make me an offer...

    I finally stuck the 5 button dic in. Plugged up the temp sensor and compass and calibrated it and bam... easiest upgrade ever. Still got to find a dealer to reset the odometer so it will pick up my bcm milage so wish me luck with that. If anyone else has had this done in western KY please chime in...

    Going to do the hud install in a few days. I've got to replace my windshield so I'm just going to cut it out myself so I can install the hud then call the glass guy to come swap the good one out of the gtp...

    Still need to attempt to rig up the heated seats if anyone knows what's involved with that. It would be awesome if I could figure out how to put the factory buttons in my hvac unit somehow... I want them to work correctly with the built in thermostats and not burn my car down. Anyone know if this has been done?

    So one question I'm still a little unclear on... when I swap the ecm for the l36 will I need to have that ecm reprogrammed do anything? Like does it have a Vin or anything of that sorts on it that needs to be changed? I just want to make sure there are no dtcs at all when I do this. I'm highly considering doing the basic pulley drop/supporting mods when I swap everything. I'll be having it dynotuned locally with hp tuners so if think he will be able to do anything to the ecm I need done while I'm there... just wondering what to expect with the ecm swap.

    Last one for now.... doesn't the 4t65ehd have a different final drive? I'm assuming the ecm takes care of the speedometer? Just didn't know if any speedometer correction would be necessary with the swap.

    Thanks guys.

  4. #4
    Killa Bee Scottydoggs's Avatar
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    Default Re: 05 GTP swap into a 04 GT1 project... need some bcm/wiring gurus to chime in.

    ive sent out clusters for repair to ebay stores, and they also do odometer re setting, you need to fill out a disclosure form and ship it off. if you dont see your part listed for repair, start pm'ing some of the stores.

    the pcm will work, you might get a code for the boost actuator unless you take the whole harness. but that code can be deleted by your tuner.

    if you take the engine tranny and pcm it all works, if your planning to use the na tranny, then you need it tuned for the gear change, dont drive it like that, the tranny will eat its self.

    if you have inspection, you'd be best to have the vin changed, or just have the na bin tuned for the sc set up. that way your vin is already set.

    98 Buick Regal GS, F body brakes, Caddy STS wheels, tinted tails L36 bottom end, lightly ported heads, 1.95 roller rockers, headers, 3.0, FSIC, 42 lb injectors, a BrandonHall rebuilt trans, DHP tuned by me. https://goo.gl/gpV5kW

  5. #5
    Turbo is the way to go. Fivefingerdeathpunch's Avatar
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    Default Re: 05 GTP swap into a 04 GT1 project... need some bcm/wiring gurus to chime in.

    You can not swap a L67 or L36 computer in a 2004-2008 car, it will never work.

    If you mean L32 computer then that may be fine. Yes the gear ratio will have to be changed. There is a difference between the transmissions. The 4T65e has 3.05's in those years, should anyway and the 4T65e HD (non Comp-G) has 2.93 gears. If you swapped both engine/trans and the computer from the GTP into the GT body it should all work fine in theory.

    SMGPFC Member #1

  6. #6
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    Default Re: 05 GTP swap into a 04 GT1 project... need some bcm/wiring gurus to chime in.

    Yes it's a l32... my mistake I get them all mixed up. The doner car is A 05 gtp and it's all going in a 04 gt. And yes I'm going to swap the entire cradle, engine, trans, ecm, engine harness and all. Im pretty sure my current trans has its days numbered having 260k+ plus it's been showing signs lately of either a lot of shaft play or possibly drive chain... it rolls 6 inches when you put it in park... not so much worried about the engine though. It runs amazing for its mileage. I'm the 3rd owner, bought it from a close friend who bought it from the original owners and according to their tedious service records all done at a dealership there was no evidence of even a intake gasket being replaced on this thing. But I'm going to run my n/a stuff until either the engine or trans quits. When one of the 2 retires I'm going to swap it all. Might as well see if I can hit 300k in it lol. If it ain't broke don't fix it.

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