fellas

i'm about 95% sure i want to ditch 5.7 in favor of a 5.3
i have priced out the engine already.

how do i know for sure that I'm getting a 5.3 vs a 4.8?
Are there casting numbers on the block or heads i should look for?


what all do i need to do the swap into a 97 sub with a 4l60e trans?
would i need a different torque converter?

thanks in advance



Last edited by Ridinlow on Thu Apr 12, 2012 4:33 am; edited 1 time in total

Externally there's no real way to know if you are getting a 5.3 vs a 4.8. The only difference is the pistons, connecting rods and crank. Everything else is the same. IN fact, the blocks are cast (4.8/5.3). The only real way to know would be to pull the pan and measure the connecting rods. You could also try looking in a spark plug hole to see if you can see the top of the pistons as the 4.8 has flat-tops and the 5.3 has dished pistons. They did this to allow the same head to be used on either engine to get the correct compression as a cost saving measure. This way, they only had to make one kind of head.

They make an adapter ring for the trans, or you can get a conversion converter. Otherwise it'll bolt right up, and the Gen3 computer will connect to and run the 4LPOS60E. If this helps, I installed a GMT400 4L80E transmission in my GMT800 truck. I used a converter that allowed one to bolt to the other and had to use a 6.0 flexplate. You won't have to worry about getting a 6.0 flexplate for a 4L60E, the only reason I had to was the bolt pattern on a 4L60E is smaller than a 4L80E. I'd give Finish Line Transmissions a call and ask them how they'd recommend doing it. They'll probably recommend doing it with a converter and they will be able to sell you the correct one. Great bunch of guys up there.

So far as the 5.7 vs 5.3, I recently got into it with a Vortec reg cab truck and ran away from him. Mine's a 2001 2WD reg cab 4.8 that's stock other than dual exhaust (baby turbos, no cats) and an EFI Live tune. All I know about the other guy's truck was he was running Flowmaster 40s, because when he nailed his I could no longer hear mine.

If you knew the difference in stroke couldn't you just check BDC with a wire or something down a spark plug hole?

Bore scope in the sparkplug hole and check for flattops.........Lorne

That's right. The 4.8 has flattops doesn't it?

So does the all aluminun HO 5.3, but there's not that many of those kicking around.

z71gmc06 wrote:

That's right. The 4.8 has flattops doesn't it?

So does the all aluminun HO 5.3, but there's not that many of those kicking around.

So, borescope and a magnet.

I can't get at my engine or I'd check, too much stuff around it combined with super heavy storms for the next few days. Anyone have a 5.3L laying around that might be able to check the crank to see if it's marked where it can be seen outside the engine? It would need to be at the back of the block where the flexplate/flywheel bolts to the crank. If I can figure a way to get at mine without emptying the garage I'll check mine tonight.