Tires: All Wheel Drive, awd vehicles, rear tires

Question
On a all wheel astro van I had the front tires replaced and now there is a knocking sound, like the tires aren't in sequence. I took it back to the repair shop they said I should of put on all 4 tires.

Answer
Juree,

AWD vehicles are sensitive to differences between front and rear tires - some more than others.  And while I can not tell you specifically about the Astro, I think it would be wise to get 4 of the same to assure that even  future related problems don't occur - because fixing those is very, very expensive.