Lm7 swap harness question
 

I am in the process of pulling an LM7 from an 02 Avalanche and need some help. The engine is out with the tranny and I have labeled the plugs and have the harness draped over the left wheel. I want to continue to pull the rest of the harness and later attempt to build my own stand alone, but I am not sure of exactly what all I need. There are a boatload of wires and I hate making more work than I need to. I can see where the main bundle exits the firewall and enters the engine bay fuse panel. This is where I am blocked. Do I pull from under the dash or separate things here? What pieces need to come out from under the dash? If any?

Plans for the truck in case they’re needed:
70 c10 shortbox
5.3-4l60e
A/C
NO power windows, locks, etc.
Possibly an external fuel pump and 100% relocated tank.
Tach, oil, fuel, (digital?/analog?)speedo gauges, maybe vac gauge.
Run the cats and O2 sensors? Not sure here...
Install the obd2?
Very stock looking but with some get up and go.

Thanks for the insight. I feel like I’ve jumped in the deep end with no idea how to swim.

Re: Lm7 swap harness question
 

LT1swap.com is your friend. Not step by step but will walk you through what's needed and what's not as far as wiring.

Re: Lm7 swap harness question
 

If you have not resolved your issues, You might want to consult the LS forum swaps in the main menu. Dual posting is against forum rules but if you don't get an answer in a few days I don't think we would mind if you asked your question in that forum.

I can help on the inside cab wiring but I would need a schematic to help with the LS wiring.

Re: Lm7 swap harness question
 

I haven’t and have been reading the link provided, but I am VERY green when it comes to this LS stuff. I have rebuilt a few engines but I am not an engine builder. I have wired a couple trucks and farm machine but they aren’t an LS by any means. I am not sure of what exactly all I need out of the donor and would like a little more insight, specifically if anything from under dash needs to come out. I may email the guy in that LT1 site as well.

Re: Lm7 swap harness question
 

You shouldn't need anything but the engine harness to the fuse box. Some people choose to keep the box, but most don't. Is this a drive by wire motor or drive by cable? If wire, then you want to grab the pedal and harness/tac module as well.

Yes, you want the pre-cat 02's as the engine needs them to run properly. As far as having cats/post 02's, that's personal preference and local laws. I'm planning on adding cats but NOT the rear 02's.

Yes, you want to add an obd2. You can probably yank that off the donor and just cut the wires, then wire it back in manually on the C10. You'll need it for tuning or even just diagnostics, or if you want to add something like dakota digital gauges they offer an OBD connection option.

I've found the 'ls swapped square body' c10 group on facebook to be immensely helpful. Even if you're not in a square, there's tons of good info there on wiring, setup, etc. There are probably some other groups as well more specific to your truck. Another great resource would be ls1tech.com, they have a 'swaps and conversions' section.

Re: Lm7 swap harness question
 

It is cable driven. Thanks for the help.

Re: Lm7 swap harness question
 

If you have the donor vehicle, then grab the cable as well. I was able to use the donor one on my 85, just had to bend the gas pedal slightly to allow for more movement. Otherwise you can use a lokar or similar aftermarket solution.