Motor swap

Stevie29 · November 14, 2017

I have a 2004 Tahoe 5.3 z71 4x4 the motors starting to give. I also have a 99 Yukon with rebuilt 5.7 4x4, can I jus pull and drop the 5.7 motor into my 04 Tahoe? If so do I have to change out the ECM as well or is my 04 5.3L ECM compatible with the 5.7L older motor?

GrumpyGhost · November 14, 2017

I have a 2004 Tahoe 5.3 z71 4x4 the motors starting to give. I also have a 99 Yukon with rebuilt 5.7 4x4, can I jus pull and drop the 5.7 motor into my 04 Tahoe? If so do I have to change out the ECM as well or is my 04 5.3L ECM compatible with the 5.7L older motor?

Disclaimer: I'm no mechanical expert.

I honestly think your Tahoe is too new to be even kinda compatible with the o'l 5.7l. Other than paying someone to tune the computer which can cost a few pennies, I think only Chevy express vans had a newer computer setup with the 5.7l and that stopped in 2002.

2003 was when GM made the big move of changing computer systems and wiring around on these engines. If you had a 2002 or older Tahoe you might have been in a better starting position to do this swap. Only other tune to go off of is a Corvette 5.7l tune, but I'm pretty sure the Vette 5.7l and your Tahoe 5.7l are different animals all together.

Secondly, I know you didn't give a description of how you know your engine is starting to die? But I've seen the 5.3l engines run for 300,000 miles plus with really minimal upkeep. I have 190,000 on my first year for the genIII engine and besides a little ticking on start up, runs like a champ. (Ticking noise is common on these engines). Maybe trying to solve why your current engine is not running so well would be a better cheaper and less of a headache option. Usually,(not always), a little head work or new intake seals (maybe lifters), new sensors and these engines come back to life.

The Bottom ends of these engines are pretty stout. Especially if you have a genIV engine, lots of guys throw turbos on the stock engines and run them. Make all kinds of power and the engine lives for more than a pass or two on the track haha.

Not saying this swap isn't doable, but I doubt it can be done for less than just finding a new genIV 5.3 from a junkyard for your ride or even a 6.0 upgrade! Just my 2 cents. Not knocking you down, good luck with the endeavor. I would kinda like to see a 5.7l swapped Tahoe.

Also I could be completely wrong, I think the Silverados sold in Mexico had 5.7l engines in them until 02 or something like that, so this could more easily done than I have knowledge of, but I still doubt it.

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Stevie29 · November 14, 2017

Thanks your probably right. And the 04 problem is the head is cracked and coolant is leaking into motor and since the 5.7 probably not compatable I might jus have to rip apart the 5.3 and replace the heads. if it was compatable I would of jus liked to get the bigger motor in it instead of replacing heads.

GrumpyGhost · November 14, 2017

Thanks your probably right. And the 04 problem is the head is cracked and coolant is leaking into motor and since the 5.7 probably not compatable I might jus have to rip apart the 5.3 and replace the heads. if it was compatable I would of jus liked to get the bigger motor in it instead of replacing heads.

Well heck, the engine should be nice and clean and all the sludge and carbon gone ha-ha, I'd try an find some stock used heads and toss them on. Use new GM head gaskets as any other brand won't hold up, I think they run $40 per side. Will need new head bolts as well, I'd just go with Chinese ones over one time use stock GM headbolts. (chinese = eBay headbolts)

If you want some power while your doin all this, I'd find some 243 heads, have them milled at a shop( I think they'll take off like 0.30 or 0.40 to get back to stock compression) , usually around $100 for both, get some new lifters and trays from an ls7 (I think maybe do some research before taking me at my word on this) and throw in a ls6 cam.

I'd only replace your rods if they are bent or you see some worn out ones, usually just roll them on flat surface and if they are straight, run em. Get a tune from a shop for best performance after doing this (blackbear does mail order tunes), but your stock tune will run it just fine. Less fuel mileage with route and the trans will need a new stall to live a longer life.

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Logan Lanfear · November 14, 2017

It'll be easier to get more power out of the 5.3 compared to any 5.7. You would have to completely change the wiring and ECM as they don't match at all between the two trucks and engines. A head job on a 5.3 is nothing compared to swapping in the outdated 5.7.

Stevie29 · November 14, 2017

That's what I might have to do thank you for the advice. Looks like I'll get the 99 running then dive it while I tear this one apart. The 99 needs a new coil pack or ignition switch then it will be up and running