4L80E swap electrical questions

[TommyM]

I've got a rustbucket beater donor '91 V2500 for the 4L80E swap into my '90 V2500. I've had the tranny rebuilt, and I'm ready to get it all put together.

I'm gonna swap the '91 ecm/pcm into my '90 to control everything. The pinouts on the connectors are in a totally different order, and of course, the '90 harness is missing the trans control wiring.

My question is what to do about the wiring. I'm considering two options:

1) swap the entire pcm/engine/trans wiring harness, which runs from the ecm, through the firing wall, to all the stuff outside.

2) keep the current harness in my '90, swap around the pinouts on the ecm plugs, and run new wires for the trans circuits.

I'm leaning strongly toward swapping the whole harness over, because it seems like it will lead to fewer cuts/splices, etc.

Any opinions as to which one is easier, faster, or leads to fewer headaches? Has anybody done this?

Thanks,

Tommy

 

[dyeager535]

Swap the harness. If you ever need to diagnose issues (wiring or not), spliced in wires will kill you.

 

[TommyM]

That's what I'm thinking.

So has anyone done this swap? Or, to you TBI conversion guys, how big a pain is it to swap an entire engine harness? As I look it over, it seems like not that big a deal.

Tommy

 

[dyeager535]

Engine harness is relatively easy. Question is, does the fuse panel differ on the 4L80E trucks, necessatating that to be changed. The interior is the real pain.

 

[TommyM]

No, according to alldata's wiring diagrams and stuff, which seem to be mostly correct, the fuse panels are the same. I've taken enough of the donor apart to see that, when you unplug the two plugs from the ecm/pcm, the wiring bundle goes straight through the firewall except for one small bundle that goes through a ten-wire connector and then runs toward the driver's side of the dash.

I DO know that that ten-wire connectors are different between the two, so if I swap the harnesses, I have to sort that out. It looks like mostly the same wires, just scrambled in the connector for some reason.

There will be some cut-n-splice no matter what. I'm okay with that, I'll solder everything just because that's the way I am. But still, it'd be nice to keep it as simple as possible.

 

[dyeager535]

Shouldn't need to cut and splice if the connectors are the same. Just de-pin the wires and replace them. All the cavities/plugs have the numbers/letters cast into them to make ID easy.