How to replace rear wheel bearing
Here's a link to anwer your question...http://www.astrosafari.com/viewtopic.php?f=108&t=11827
if you never did this before get a repair manual if you want to do it yourself. its not really that hard to do. a shop will charge a few hundred for a job like this.the bearing are only about $15.00 ea. good luck.
Search Chevrolet Astro Questions
Are you a UK consumer? CarGurus now has a discussion forum in the UK.
Chevrolet Astro Experts