Clunk heard from transmission while driving
 

Since I have owned my blazer (it had 150K and I've owned for about 3 - 4 years) it has had a clunk heard from the transmission that only really happened when it was shifting from 2nd to 3rd, but more recently I am now hearing a clunk heard when going from 1st to 2nd, 3rd to 2nd, 2nd to 1st, and when tc clutch is applied and released. I've read a couple of tsb's for 2nd to 3rd clunk, but that was when I got the truck.

Is there any information on what the concern could be? Or is it a sign that transmission is banging its death drum?

Also, the fluid level is good and does not appear to be burnt. The fluid has been serviced (not flushed) with a new filter every 10,000 miles since I've owned the truck and the last service was done about a month ago and the magnet had only couple of thin lines of shavings (almost nothing).

Well, I know what's wrong and found out in the worst way possible. The transmission gave out. I put the truck into reverse just to get it in the shop and a loud bang later no reverse. It has first gear, but I didn't try to drive it on the road. Now it's stuck the shop and I need to figure out what to do.