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1987 K5 6.0 swap with a 4l80e transmission. Need help with electronic integration with the truck

Johnd1987

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I won’t have a problem with getting the engine in the truck. I’m not sure how I’m going to get all the computer and wiring to sync with the truck. Any information on parts or tips to do the swap would be awesome. Thanks
 

Bent77

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What are you doing for a transfercase?
 

Johnd1987

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What are you doing for a transfercase?
That’sa great question and I’m not sure at the moment. I have the one that came attached to the 4l80e out of a 2001 3/4 ton suburban with the engine. Do you know what is compatible with the 4l80 and will work in the blazer?
 

smackem

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Full disclosure: I haven't done this swap into my 87 K5 yet but I am finishing up a 6.0/4l80 swap into an 89 ramcharger, so I'll share what I've learned. As far as the wiring, do you have the intact wiring harness and computer from the 6.0/80? Do you want to reuse that or use an aftermarket harness? There are advantages to both, namely time vs. money. You can rework the harness yourself using the diagrams at Lt1swap.com. Or you can buy an aftermarket one and it's plug and play. Note that different harness builders place the PCM in different spots. Some put it inside the cab, some keep it in the engine bay similar to OEM. If you've got a preference, keep this in mind. When you take the original engine out of your K5, label all the wires as you disconnect them and lay them aside. Don't cut anything yet. Less than half of the wires coming out of the bulkhead connector will need to be modified. The majority feed lights, wipers, etc. so you don't have to touch them. Here's a link to a pretty helpful video:

As far as the above question regarding the transfer case, you can use the 208 that's in your k5 now, you just need an adapter plate. Novak, Advance Adapters, and many other places make them. There are lots of good vids on the swap and parts on the aftermarket to make it smooth. Keep in mind frame clearance when you think about headers especially with aftermarket engine mounts. I believe the 87 has a baffled fuel tank so you should be ok to just put in a high flow pump and regulator and your fuel system should be fine. Double check to be sure. Remember that if you change the drivetrain placement a lot your driveshaft lengths will have to be modified, so try to get it as close to the original placement as possible to save some cash.

Remember that it won't crank until you get the PCM flashed to take out the anti-theft stuff. You're going to run into a lot of problems that you didn't see coming but nothing that can't be overcome. Keep working and you'll get there. Hope this helps.
 

Johnd1987

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That’s a lot of great information and I really appreciate it, thank you. I’m going to be pulling the old 350 out pretty soon and probably would have done it like a hack. I will definitely be taking my time with it now. Also I do have the full 6.0 wiring harness and PCM and I think I will be trying to make that work unless I run into some major complications.
 

Chuy84k5

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look on YouTube for a guy called the puppet kicker Lenny has some really helpful vids on square body ls swaps and as far as t case I have a 4l80e witha 241c with electric speedo on mine. but I also have a set of autometer invision gauges
 

bix

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Hey, i just put a 5.3/4l60e into my truck, i am using a holley ecm but if theres any questions id be happy to help! I didnt know much about the wiring at all, and just kinda went through it.
 

bix

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the bulkhead wiring seems daunting but its pretty simple as its broken down ( and explained in the video above )
 
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