Jacob Benson

I have a 2002 suburban 2500 2wd with the 6.0, and quite a few 5.3 1500's sitting around. Everything runs great. But the 6.0 is a gas guzzler and on its last leg. I don't really want to rebuild the 6.0. I love the mileage I get from my flex 5.3. On the highway it gets the same milea free my Cobalt does. Problem is the 4l60's in the 5.3 are complete garbage. I'm wondering if I can swap the 6.0 for the 5.3 flex, and still keep the 4l80 and heavier axles and suspension in the 2500. And if I can swap it, what all needs to go with the motor? I assume I need to keep the computer with the motor because that's what tells the motor to kill half the motor at highway speeds. But what else will I need to keep/swap out? The 6.0 has oil everywhere at only 200k miles. Yet two of my four 5.3's have over 300k, with not a drop of oil on the outside of the motor. As a matter of fact, my 01 5.3 2wd has 380k on it, and is the quietest and most powerful/responsive engine I have. It is not a flex tho, it's fuel mileage is about half what the flex gets. I get 28mpg out of the flex on the highway. No bullshit.

gagliano7

The 5.3 will swap right over. Of course you will have to have it tuned. I hope you don't get your hopes up because the 5.3 with that 2500 drivetrain will have less power than the 6.0.
You might do a little better mpg but i doubt it. The 2500 are also heavier than the 1500's and the drivetrain robs more power than the 1500 drivetrain. The 2500 is probably 2500-3000 lbs heavier than you 01 2wd 5.3.

Swap wise it is really simple since the blocks are the same size and everything will bolt right up.

Jacob Benson

Thank you for that info. I also found a 95 3500 crew can pickup with a 454. Price is pretty steep on the truck but the 454 would definitely work better for me than the 350. I would much rather have a diesel. I havent pulled the trigger yet on anything. I just know that the transmission in the 5.3 will not take too much Camper or car trailer hauling.

Jacob Benson

Ok so I just realized that the 350 is a 5.7L. So I did a little research on my sub. And found that the 6.0L vortec in it is actually a 364 ci. Never heard of this ci before so I assumed it was 350. Question is, this should still be a small block, will the transmissions still swap with the 350 and 325/323?

gagliano7

All the LS blocks are the same size. Even the 7.0 LS7 would bolt up.