Gorilla72

Hey guys, I am wanting to do a 5.3 swap into a '94 wrangler. I found a low mileage 5.3 engine with a 4L60e trans. The seller doesnt have the wire harness nor the ecm. My question is will any ecm or wire harness work if I get one from the junkyard? I believe the motor and trans are from a silverado. He is asking $600 for both.

I found another motor and trans with harness and ecm for $600 but the its got $150k on it and has a rough idle. He has video of it running before he pulled it.

Any guidance would be appreciated.

Kawabuggy

iTrader: (1)

The PCM & Harness MUST MATCH the engine..! There are 24X and 58X reluctor rings inside the engine on the crankshaft. You can't interchange them! Find a harness, and PCM from the same year as the engine you intend to use. This is smart way to do it. I'm sure you could make any computer, or harness, work but it will take significant changes in programming, and wiring, to make that happen.. Better, and cheaper, to just start with the components that match your year of engine. Keep in mind in later years there is DOD, and VVT to think about. Can't use an early computer & harness on one of those engines! I would buy the second deal @ $600, and then re-sell the other motor, or keep it for a spare build. $600 is a great price for engine, trans, harness, and PCM.

B52bombardier1

Yes, great deal and good advice above. A GMC Sierra truck of the same year will also work for a donor harness.

Rick

Gorilla72

Thanks fellas. Well turns out the first guy only has a trans with 62k on it. No motor. *bummed*

The second seller with motor and trans for $600 isnt quite sure he has a PCM or wire harness. Waiting for his confirmation yet.

So as long as its the same year truck, it will work correct?
The second seller says its an 05 motor and married trans with 150K on it. I was recently at a local junkyard and saw a 05 silverado with severe front end damage to it. But was thinking I may be able to get the wire harness and pcm if its located on the drivers side cab side. The passenger side was hit so hard that you can see the motor just looking at it. There isnt a fender left. Cant get the mileage on it though.

I also found a GMC Envoy V8 but the wire harness was cut. Looks like it can be spliced back together as both pieces are there but being a junkyard vehicle it looks like ppl were poking and prodding at it. Its missing some stuff. Again cant get any mileage off it though.

Gorilla72

Will I need the fuse box from under the hood and in the cab?
I got some photos of the motor and trans. I see wires running all around it. Are they the only wires needed?

B52bombardier1

While you could use the original fuse box from the original LS engine donor vehicle, most people leave that alone. In your case, you most likely have enough capacity in the 94 Wrangler fuse box to make the swap happen. You really only need four wires to support the LS engine's power needs:

1 - full time 12 volt power to the memory keep alive wire inside the PCM
2 - ignition key hot power to actually power up the PCM - this is different than "1" immediately above.
3 - fuel pump power
4 - electric fans power if using e-fans to cool the radiator

Go to the LT1Swap.com web site for further guidance.

Rick