I just installed a rebuilt 5.3 into my 01 ECSB. Flat top pistons, 243 heads and a z06 cam. Now that i have 2k miles i took the boat out (3000 lbs) and going up some steep hills could only do 50-55mph in third at 4500rpm's. Truck went up that hill much better when i had the 4.8 in there. Is the cam the problem or something else? Installed 4.10 gears also.

 

The cam isnt the perfect pick, but still it should have quite a bit more power/tq than the stock 4.8.

Who tuned it?


ive pulled 8-10k # trailers with my 5.3 back when it was stock and it didnt have any problems like that, something is up..


Whats your transmisison temps?

 

4500rpm in 3rd only going 50-55? That does not sound right at all. Did you retune? Aftermarket converter? The LS6 cam will move the powerband up a little bit, but not that dramatically.

 

thats why i asked bout trans temps..
4.10s in 3rd with a 30" tire should be 100mph no converter slip.

Sounds like the transmission is goin out or something is up..


2nd gear at 4500 should be roughly 60mph

 

This. Something is way off. I had 4.30s w/ 30" tires and my RPMs werent anywhere near this bad.

 

now if it was 2nd gear at 4500 that would make more sense, but it should still pull a 3k# load pretty easy with 4.10s!

 

Agreed, something is out here. A 5.3 would out tow a 4.8 any day given that set up.

 

Toward the top of the hill the tranny temp hit 190-200 so not bad there. the engine temp hit 250-260. The transmission has 135,000 miles on it. The guy who built the motor did a mild tune and said he would do a better tune once i had 3000 miles on it. The MAF was dirty and kicked off a P0171 code the other day. Would that account for the lack of power?

 

250-260*?
you got a problem there or that was one crazy steep hill!!

 

also i have the LTZ wheels from a tahoe