Looking for help to why I made it 40 miles just fine in my 2002 gmc envoy stopped for 20 minutes started back but at third stop light wouldn't go into 3rd stopped to think / check tranny fluid all good started again now won't go into 2nd after being towed home I had to reverse a bit to get where needed and reverse grabbed fine moved a few feet went to move forward 1st went out now no gears including reverse are grabbing at all just engine rev like in neutral. Hours later asked son if him and friend would push it off the grass of coarse 19 he had to try gears himself and 1st and reverse worked again at least for a moment then stopped. Where can I start looking. Do I have hope or is it sound like probable rebuild or more?