well the 5.3 took a **** on me 2 weeks ago, so i installed an 03 lq9 in my ext. cab and it put down on a dyno jet 312rwhp and 348rwtq. mods are cai, edelbrock shortys, and a borla xr1 muff and tuning. i quite happy with the power gains. the old motor put down 282rwhp and 287rwtq on the same dyno.
the mods on the 5.3 was a 04 z06 cam and home ported heads, cai, and my borla through the stock manifolds

 

I was thinking of doing this to my Avalanche. My question is did yo have to beef up your tranny?

Kelly

 

Just to swap engines, it is not necessary.

If you want to the tranny to last any amount of time, it would be a good idea.

OP- throw some long tubes on it and get it tuned. It will respond nicely.

 

last year my 4l60 lost 3rd and 4th gear so i had my buddy rebuild it with better internals and vette servos. i didnt go with longtubes cuz i wanted to have a reliable truck that i didnt have to dick around with to smog it or whatever.