I just bought a high mileage 4.8 SCSB truck. I plan on doing a few dyno tech articles for my website using this truck as the test mule. Anyway, I was driving it the other day and stopped on a slight hill, when I pulled out the tranny started to slip badly. I then noticed that if I took off normal the tranny felt fine but if I left the line hard it would slip badly then all of sudden grab and take off. It felt just like the rear wheels were spinning then grabbing. If I took off in second it would do the same thing. The tranny felt great any other time but slipped bad when leaving from a dead stop. I checked the fluid and it was way overfilled, I mean way over filled so I decided to drop the pan and change the fluid. When I pulled the pan the filter was in the pan and not on the valve body, it had come out. I got to looking and whoever changed the fluid last time used the filter made for the smaller flat pan, my truck had the deeper stepped pan and needed a longer filter. Installed new filter and fluid and problem was solved. Just a little FYI in case someone else runs into the same problem.

 

Congrats, nice find. It sounds to me like whoever did the filter change messed it up, and to fix it kept adding oil until the tube where the filter is connected was submerged in oil.