I have a 2005 Chevy Avalanche 1500 with 4x4. My transmission is shot and needs to be replaced. I currently have 146,458 miles on the engine, and figured I would replace the engine and transmission. I am looking to replace the engine with a 383 stroker engine however I don't know if the engine and transmission determine if my truck will still have 4x4. can someone please help me out. I was thinking $12,000 for new engine and transmission plus labor, but before I do it I wanna make sure I will still be able to have 4x4.
tl dr: As long as you replace it with an LSx based engine and 4L60e transmission, you will have absolutely no fitment issues with the transfer case and retaining your 4x4.
Only the internals of the engine would change. Externally the engine will remain exactly the same. You're going to need a new block to do this, however. The LM7 engine (most common in your year of truck) does not have the capability to be bored/stroked large enough to get to 383 cubic inches. More than likely you'd need an LQ4 or LQ9 block, then bore and stroke it to size. Most LSx blocks are aluminum and can only take a small amount of boring (0.010" MAXIMUM) before they need to be re-sleeved.
Your 4L60e transmission will most likely need to be rebuilt. If you rebuild it over replacement (most common), I'd suggest you opt for the higher capacity aftermarket parts. One of the key parts to get upgraded is the sun shell, as this is a relatively weak part in the 4l60e. A stroker engine will produce a ton more torque than what you're used to, so just a stock rebuild will not deal with it for very long and you'll end up replacing the transmission or fixing it again soon. Another consideration is ensuring you get a torque converter which is matched to your engine output. If you don't increase the stall speed even by a little bit, you'll find your engine will be a dog.
And don't worry too much about the transfer case itself. Nelson Performance out of Texas (I believe) has told me they twin-turbocharge engines in 4x4 applications of the LSx based trucks, putting out over 1200hp, and see no issues from the transfer case. Should not be an issue with just a stroker engine.