Quick question guys, any help would be appreciated.

Whenever I am moderatly accelerating going from 2nd to 3rd, it feels like it slips back into 2nd then back to third. It only does it when I am at about 1/2 to 3/4 throttle. If I manually shift it, it doesn't happen. I can't seem to match up this to any troubleshooting symptoms in the book. Any suggestions?

 

Could be the torque converter un-locking to give you alittle extra power, then locking back up again....