97 2500 Chevy

[dj_97]

Okay guys. I’ve got a 97 3/4 with the 5.7. The engine is trashed. Both heads were cracked severely. I bought a 96 Yukon with a good running 5.7. My harness on the 97 has been cut and is missing some pigtails. Can I use the 96 Yukon harness? I know the ecm is different (97 has a 4l80 96 has a 4l60) but I want to just set engine harness and all in the 3/4 if possible. Any help is GREATLY APPRECIATED!!

 

[dj_97]

Also, will the fuel tank work? The 97 doesn’t have a tank. The Yukon doesn’t have the little square rank it has the oblong rectangular fuel tank. I do know the sending unit is different, just curious if I can change sending unit and use the tank?

 

[kennythewelder]

The plugs at the trans are different, everything else is the same I think. The transmission shifts are controlled by the ECM, not the harness. As for the fuel tank, I would think so.

 

[dj_97]

The plugs at the trans are different, everything else is the same I think. The transmission shifts are controlled by the ECM, not the harness. As for the fuel tank, I would think so.

Okay potentially just change the plugs for trans and should be good? Ecm is different also correct? Wondering if I could use Yukon ecm or have to order one

 

[kennythewelder]

The ECMs are just programmed different. Ether one can be reprogrammed to run whatever. They should plug into the connectors, but will need to be reprogrammed to run whatever your running. I haven't tried to do a 4L80E swap, bit there are people on here who have, and can tell you what the difference is between the two.

 

[dj_97]

Who would I look into to program it? And would it just not shift or not shift properly? I’m used to TBI and carbs so this ones new on me lol

 

[stutaeng]

You'll have to get another harness that came with the transmission your truck has. Although the Tahoe harness can be modified, it involves repining the transmission connector and the ECU.

I'm assuming the ECU of the truck is okay, right? Leave that alone, then there's no need to reprogram anything.

So just a harness should be pretty easy to source.

BTW, the 2500 truck 5.7 is a bit different than the half ton 5.7 internally. 4 bolt main, and some other minor things. I'm not sure if it matters...

 

[dj_97]

You'll have to get another harness that came with the transmission your truck has. Although the Tahoe harness can be modified, it involves repining the transmission connector and the ECU.

I'm assuming the ECU of the truck is okay, right? Leave that alone, then there's no need to reprogram anything.

So just a harness should be pretty easy to source.

BTW, the 2500 truck 5.7 is a bit different than the half ton 5.7 internally. 4 bolt main, and some other minor things. I'm not sure if it matters...

Replacing a connector wouldn’t bother me too bad. The truck does not currently have an ecu. I assume the previous owner took it and cut out the connectors for another truck. It doesn’t have either. And so far I have no luck just finding a replacement harness for it. That’s why I planned to use the Yukon harness and order a ecu programmed to the 2500 vin #. It won’t be used to pull anything huge or heavy, mainly a bass boat and gooseneck camper occasionally or occasionally a flat bed trailer.

 

[dj_97]

You'll have to get another harness that came with the transmission your truck has. Although the Tahoe harness can be modified, it involves repining the transmission connector and the ECU.

I'm assuming the ECU of the truck is okay, right? Leave that alone, then there's no need to reprogram anything.

So just a harness should be pretty easy to source.

BTW, the 2500 truck 5.7 is a bit different than the half ton 5.7 internally. 4 bolt main, and some other minor things. I'm not sure if it matters...

This is why I’m replacing the harness. You can see where the ecu is supposed to be, along with the connections

 

[stutaeng]

Ok, I see.

I did a NBS 1500 4L80e swap, but I don't know how that differs on the OBS. I seem to recall the OBS has 2 connectors per side, but later they lumped 2 connectors together. I'm talking on the ECU side. You'll need a ECU pin out for your truck. A guy name @Lextech here used to get them...but sure if he's still active.

On the transmission connector you can see my thread on the LS + Carb Swaps and hopefully it's the same for you year. I'm guessing it is because the electronics of those tranmissions we're all the same. But double check first.

Good luck.