I have a 2000 Pontiac Grand Prix, 3800 V6 with an auto transmission. When the tranny gets hot, it will (only sometimes) whine and clunk into gears. Let it cool and no problem. I can drive freeway at 80mph all day, but then hit a couple of stop lights and it will clunk. I took it to a tranny guy who drove it for 1/2 hour and could mot get it to error on his scope. We serviced tranny, but it started to clunk again. I noticed today, when hot , the whine I hear is present even when the tranny is in park. What up with my tranny? Any fixes?

Drop and clean the pan, change the filter, and refill with Mobil 1 Synthetic ATF. Follow the procedure below to completely change all of the fluid:

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