Engine Swap on Silverado

Jman423

Original poster
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Mar 24, 2014
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My buddy is getting ready to swap engine/trans from a 2005 Silverado 2500 to a 2007 Silverado (Classic). He has engine smarts, but like me, he never really got into the whole computerized engine era. Give him an old S10 or a Bronco and he'd be able to go to town with the right parts and tools available.

Anyway, I believe he is going from a 4.8L V8 to a 6.0L V8, including the trans. What kind of curve balls could he possibly encounter? Is it as simple as keeping the PCM/TCM with the correct engine, or will there be differing computer types/harnesses and so on...? I'm guessing the BCM's will differ, further adding to the mess.

So, anyway... any input would be helpful in the planning stage.

Thank you!
 

Mooseman

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Dec 4, 2011
25,257
Ottawa, ON
Silverado Classic meaning the Old body style? I would think that it would be the same between those years as it would just be carryovers from the 2006 until the New body style came out a little later. If the PCMs are the same, the 6.0 should slip right in. Transfer the wiring harness and PCM from the donor. Might have to tune the PCM to play nice with the BCM but I would turn off VATS as that might not like the year differences.

Mechanically, I would also look at replacing the diff with the bigger one from the 2500 or from a 6.0L 1500 to avoid mismatched front and rear bolt patterns (6 vs. 8). If using the 2500 diff, I don't know if it's possible to swap the front suspension components using the 2500 stuff. The original 8.6 rear diff may survive but there's a reason GM put in the 9.0 behind the 6.0L.
 

Jman423

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Mar 24, 2014
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Silverado Classic meaning the Old body style? I would think that it would be the same between those years as it would just be carryovers from the 2006 until the New body style came out a little later. If the PCMs are the same, the 6.0 should slip right in. Transfer the wiring harness and PCM from the donor. Might have to tune the PCM to play nice with the BCM but I would turn off VATS as that might not like the year differences.

Mechanically, I would also look at replacing the diff with the bigger one from the 2500 or from a 6.0L 1500 to avoid mismatched front and rear bolt patterns (6 vs. 8). If using the 2500 diff, I don't know if it's possible to swap the front suspension components using the 2500 stuff. The original 8.6 rear diff may survive but there's a reason GM put in the 9.0 behind the 6.0L.
Yes, 2007 Classics are early model year body styles.

Which harness are you referring to swapping out? How involved would it likely be?
 

Reprise

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This should be about as straightforward a swap as it gets, tbh. Google '4.8 to 6.0 swap', and there'll be a few different leads to read up on. Videos, too. Not saying it'll be "plug & play", but it shouldn't be difficult.

There's a good chance you'll be able to leave the existing harness in place, especially if both trucks used the same PCM (P59, most likely). There were two different versions, one with 'red' and 'blue' connectors, the other with 'green' and 'blue'. The red/blue is a drive by cable, and the green/blue is DBW. Since '03+ is DBW, you should have the green/blue on both harnesses. Note that if you're going from DBC > DBW, that the accelerator pedal assy has to come over, as it's part of the DBW. But this is unlikely, since both trucks are +03 MY.

If the '05 donor was already set up with e-fans, you should be OK. If not, you'll need to add two pins in the '05 PCM connectors (one in each). I have a thread on this, and you can likely do a comparo between the two PCMs as well, to see where to put the pins. It also needs to be updated in the PCM (also in my thread); you'll need tuning software for that.

If the new trans is a 4L80, remember that it's a little bit longer than the 60 that's in the '07. If you can get the driveshaft(s) from the '05, it may save you time / effort.

Steering components will likely differ, which may affect the fit of the front diff, if you're swapping that. The '05 may have recirc ball, while the '07 most likely is R&P. Just make sure you've got the room to use whichever setup you're going with. Also, make sure the t-case 'drops' on the same side on both, or you'll need to account for that.

That's all I can think of, off the top of my head. And I'm sure there's something I've left out. But that should hopefully get you 'closer to bright'.
 

Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
Which harness are you referring to swapping out? How involved would it likely be?
The engine harness. As per @Reprise 's post, you might not have to swap it. If that's the case, you're golden.
 
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Jman423

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Mar 24, 2014
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Great, thank you for the info.

Unlike Ford, I suppose it won't be easy to modify/tune since software is all licensed and you have to really know very well what you're doing.
 

Reprise

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Jul 22, 2015
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If his engine is stock going in, then it should be covered by the corresponding PCM. That's the beauty of it.

Even if the e-fans aren't brought over, you could rig up a mechanical fan clutch and roll with that for a bit, till you found a local tuner. Or Limequat could help, I'm sure. As could I, but Limequat has much more experience than me :dunce:

Both of us use HPTuners, btw, and I think that's the preferred option for GM / LS-type engines. If I were using a standalone solution, I'd probably go with a Holley system, because they're so simple to hook up, and they eliminate the guesswork, while still being tunable. They're hella expensive, though, especially compared to an OEM PCM.
 
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