Recently did a simple pan drop and filter change on a 4L60E transmission. Ever since, it's been doing something I've never seen. Start engine, select drive and take off. Shifts smoothly and normally and has no issues....UNTIL you drive it for about 20 min. Then it starts shooting fluid from what appears to be around the front of the pan gasket. It's almost like there's an excessive pressure build up forcing fluid past the pan gasket. Pan bolts are tight. Even swapped the gasket a second time to make sure it was good. DOES NOT happen until its been driven for about 20 min. This thing operated perfectly fine until I serviced it. What would cause this after a routine, simple pan drop and filter change? Here are the steps I did...very routine. Done this a few dozen times over the years. 1. Removed bolts, shifter cable bracket and dropped pan 2. Pulled out old filter and pickup sleeve insert 3. Cleaned pan and magnet 4. Installed new pickup sleeve insert (tapped in with same diameter socket until it bottomed out in its bore) 5. Installed new filter (pushed up until seated) 6. Installed new gasket on pan, installed magnet to the same spot inside the pan and reinstalled pan 7. Topped off fluid and road tested...rechecked fluid level...everything looks good. No leaks anywhere. There were zero issues removing or reinstalling anything. Could be pure coincidence this started when I serviced it? Even so...what would cause one to force fluid out after 20 min of normal driving?