I have a 2004 chevy rcsb, 4.8l, 5speed manual. I'm wondering what rear i have in my truck? I'm looking to do a GTO 5.7 LS1 swap, can my rear hold the extra power? Any information will me greatly appreciated. Im a noob lol. Thanks -Sean

 

You'll probably want some 3.73s or 4.10s and some kind of positrac with the bigger engine. The axles and casing should hold up just fine, an LS1 isn't going to kill you're rear end. There's guys running larger motors just fine.

 

look at the RPO codes in the glove box...you'll find something like GT4 or GTU and that will be your gear ratio...let us know it says in the glove box and we can tell you your gear ratio...

if your just doing the swap with even a cammed 5.7, the 10 bolt will be fine...but a trutrac in it and enjoy

:EDIT: I just found this in a quick search for you

GT4 -- AXLE REAR, 3.73 RATIO
GT5 -- AXLE REAR, 4.10 RATIO
GU4 -- AXLE REAR, 3.08 RATIO
GU5 -- AXLE REAR, 3.23 RATIO
GU6 -- AXLE REAR, 3.42 RATIO
G80 -- AXLE REAR, LIMITED SLIP (POSITRACTION)

 

since its a 4.8 rcsb its probably a 3.23 or 3.42.

 

my 4.8l 5 speed was 3.73s from the factory, but it was an ECSB

 

ahhh thanks alot jake brake ill look now

thanks for the help guys!!!
-sean