tranny question

1999 LTZ with 3.8.
recently my tranny has been a bit strange. at random it will start to shift hard between gear. and than while at about 40 mph, it will shudder a bit. and you can hear a whine from tranny.
If i pull over, turn car off, than resart it problem goes away.
No check engine light or anything.
Getting ready to do filter and fluid change. Is there a selinod hanging up somewhere.
I saw a post on here, about a similar problem, but I cant find it.

Thanks
Paul

Well, about 40 is usually the threshold for the TCC to command lockup, if cruising on flat road, and the shudder would be typical of the TCC when malfunctioning. There isn't usually noise associated, though.

Anything else you can think of that might be helpful?