2004 Suburban: I feel a vibration around 30 - 40 MPH. If I let off the gas, it goes away. Heard a clicking noise a couple days ago, but have heard it since. Maybe drive shaft or u-joints?

 

does it get worse if you go faster? but yes ujoints would be 1 of the first things id check

 

I changed trans filter and fuild. Vibration goes away around 45 mph.

 

got two codes p0171 and p0174. checked MAF. OK. Could this be causing my shudder? Maybe vacuum leak?

 

sounds like you're chasing a few problems at once or just not thorough in your posts but yes if your fuel pressure/volume are ok and you have both banks lean theres a good chance you have a vacuum leak...probably intake manifold gaskets

 

Checked joints. Front cups are crushed. I need a good video on removal. Thanks.