97 GMC Sierra 5.0l soon to get a full 5.3l swap..

I forgot to add that I have to add in an OBD-II plug in order to scan for codes.

IIRC you also need to keep the wires for your tach

Yup, that's one I forgot, hahaha. I'm telling you, if I do another swap...I'm going to buy the pre-made harness from someone. It's just so much quicker. Well, Ecu is off to get reprogrammed. I can't wait to get this on the road.

I do have one concern, my 4.8l exhaust y-pipe looks like it might hit my trans cross-member. Anyone have any input on this? I think most everyone uses a set of "swap headers".

Yep, I'm using swap headers also. Honestly your best bet is to have a y pipe made

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Originally Posted by pacobeagle

It's somewhat complicated as I simply added a bus to my OEM fuse box and tapped into the power for all of the new items there. I also tapped into the OEM fuel power supply and ignition power supply from the fuse box. Essentially, I've still got the fuse box but with i think two or three added fuses. I can't remember right now. I've grafted both harness's into one. I've removed a bunch of grounds from the harness. If needed I can always add to them.
As far as keeping items from the OEM harness....I kept the starter signal, oil pressure switch, a/c, coolant temp, alternator wires. I also have to make a "y" harness for the speed sensor as it needs to go to the new ecu to deal with shifting the trans and it needs to go to old ecu for gauges. Theres more I'm sure, but my brain is fryed right now in dealing with al of these wires!!!!!

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oh ok..so you kept the original fuse box and just added the extra fuses for the ls stuff. where does the vss go?

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Originally Posted by silverado_lover

Yep, I'm using swap headers also. Honestly your best bet is to have a y pipe made

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true duals!!

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Originally Posted by myzterray

oh ok..so you kept the original fuse box and just added the extra fuses for the ls stuff. where does the vss go?

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I was told that VSS must go to both new and old ecu. The new ecu needs the signal for shifting duties, and the old ecu for the gauge.

Well, the ecu and Lextech's a/c bracket kit are on their way to me. Really excited to get this on the road. Going to have to drive it "open header" to the exhaust shop in order to get the Y-pipe cut/modified/welded on. Should be pretty nice. I've already got a Flowmaster 50-series I scored from the salvage yard in there for $15!!!!

Bolted up the OEM(2000) Y-pipe and there is a small problem. The cross-pipe(from drivers side over to the pass. side) goes right under the trans. mount!!!! Either I chop/cut and modify the y-pipe or I custom build a new trans cross-member. I'm thinking plan "B" for right now. Going to have to find some 3/8" flat bar at least...maybe some box tubing.

Sunday update:
Found at the salvage yard the NBS trans cross member($17). Also found a pair of 10-bolt, 6lug rear axle shafts($19ea). I didn't purchase the rear axles because I am not really sure that they will work. My question is about the rear brake drums. Can I simply re-drill them for 6 lug?
I'll post a picture of the trans. mount dilemma later on today.