2008 gmc envoy denali how do u know starter is going bad

Generally starters don't give you much in the way of notice. Sometimes the starter will not fully disengage and make a metal on metal grinding noise. Often times when a starter fails you'll hear a solid single click. If you hear this it is possible to free the starter motor up by hitting it a couple times with a hammer. This is only a short term solution. Ultimately your starter will need replacement.

The ONLY way to determine if the starter motor is the culprit is through *hands-on* testing by qualified personnel. There are multiple causes of a no CRANK condition .. Posting these possibilities here is not going to help as each one will require individual hands-on diagnosis .. Furthermore this problem MUST be present before accurate testing can be performed - by anyone..