Got a 04 2500HD with the 6.0. It has a lifter tick, throws Misfire and Bay 2 Knock sensor low input as well and need to figure out. transmission is getting screwed becasue it was drag raced and after i lifted, i hit the brakes hard, hard a loud clunk or bang, and then had a handful of truck to take care of. also leaking tranny fluid.

apart from either's issues, what to upgrade first?

6.0L V8
4L80E

 

First we need to know what you plan on doing so the proper upgrades can follow.

 

Well, the engine needs help getting through the gears. It’s really slow through 2-3/3.5 grand. (Slow meaning it feels lazy until it hits 3 grandish). Right now, I’m thinking turbo, but I now there may be some things I need to take care before hand.

I also want the automatic to be a manual but that seems a little extensive for the truck.

basically I want the truck to have a pair...

 

You did say it has a misfire and knock sensor codes. Get that fixed first and then start the upgrades. A good custom tune will help that truck out. Factory torque management robs lots of torque until you get over 3 grand to eliminate wheel slippage. Basically your looking at 3-5k to do it right depending on how much boost you want. Don't skimp and get a quality waste gate. You can run around 8-10 psi without having to open up the ring gaps. Usually around 10 hp/tq per 1 psi of boost. You might pull 15 depending on what cam and valve springs you use. Vs racing put a kit together that Matt uses (sloppy mechanics) and it is pretty resonable. He ran a stock 4l80e with a stall convertor and never had a problem.

 

How is it as a diy? I’m already planning on and a k&m cold air intake as they are fairly easy to do. As far as turbo, I am thinking of a 20-30mm quickspool. I think that’ll give me the low end push I’m looking for?

 

If the intake is truly a cold air intake that sucks outside the engine bay then I am all for it. Sucking hot engine air doesn't do crap for the engine.You can flip the stock passenger manifold upside down and build the exhaust hot side there. I would go with probably a 45mm at least. More air and there are turbos out there now with no lag. You hit it and it makes whistle noises fast. Your gonna build low end torque with a turbo anyways.