I'm getting a clunking sound somewhere either in tranny or some other place.

What is your question?

a tranny shop thinks its the planet plates gears inside, but it only happens in drive and starts about 3/4 miles down the road. If I drive in 2nd or 1st it does not sound. Another tranny shop says the planet gears only operate in 2nd and 3rd. I have an automatic. To replace the planet gears we are looking at a whole new tranny job costing $1500. What if that's not it? Any suggestions?