I brought my 2001 Yukon Denali (all wheel drive) into Aastro because sometimes I could hear a squealing in the engine. They called back and said that it was a bad pulley and that my check engine light revealed that I had a dirty mass air flow sensor. I approved the work and told them to also check my front differential oil level because it had never been checked and that occasionally on the freeway with the radio off I could hear a little hum from the front. Of course, George said that the front end was bad and needed to be rebuilt. He told me... read full review »