I own a 2001 Chevy Sliverado 2500hd 6.0L 4x4 with a 120,000. The problem i am having is that my ac went out with a hiss when i had the ...

I own a 2001 Chevy Sliverado 2500hd 6.0L 4x4 with a 120,000. The problem i am having is that my ac went out with a hiss when i had the breaks on going down a hill now when i hit the breaks it nudges hard forward, and when i put it in reverse it damn near dies like 200-400rpms and rough idles is it because i am running 10w-30 instead of the 5w-30 i only run it in the summer 5th summer i have ran it? Any answers or ways to steer me anything would be very helpful.

Periods and concise thoughts are your friend. Your post was very hard to understand...

Not sure what the problem is, have never personally experienced anything like that. There are a few GM service tech guys on the forum, hopefully they will be able to shed some light on the topic.