I have a 2002 SLT 4 door 1500. 4.7 V8, 4x4. My heat and A/C are stuck on the vent setting and won't go to any other setting. Also, when you turn on either, the heat or a/c it makes a loud vibrating noise the higher you set the A/C to blow. Any suggestions?

 

Well your title reads "blend door issue" and you know you have that problem so what exactly are you asking?

Go fix your blend door issue

 

I was honestly trying to figure out if that's what the problem is. I've read other threads where people say a vacuum line had come loose. I didn't know if anyone had any suggestions

 

Not a vacuum line problem. It is a blend door problem and a common one at that. Lots of threads on here that are blend door related. I used to have two threads bookmarked from another site with full disassembly details but they don't work anymore. It's a simple fix but does require taking the dash apart