Rear axle bearings

[steppside69]

I have a question about the rear axle bearing, I was changing the rear brakes on my truck and noticed what appears to me to be ALOT of play both thrust (About 1/4-3/8") And up and down (About 1/16 + or -") I dont know if that is acceptable or I have a problem?

The truck is a 2006 silverado z71 ext. cab 5.3l
It has 80k miles and has a intermediate noise from 1st to 2nd. Sometimes it will make a clunking sound but will not do it all the time. I also noticed a slight vibration when coasting to a stop light. Thought that it maybe in the tranny so I put the truck in neutral while coasting and the vibration was still there. I hope that there is nothing wrong but my gut is saying something else, Thanks for the info/guidence
Eric