Joined: Wed May 2nd, 2018
Occupation: Elevator Design Worlds Tallest Buildings
Interests: Ranger Based Vehicles and OFFROAD
Reputation Points: 5399
|140K and 99.9% of owners = never been serviced
4r55e biggest issue is leaky separator gaskets
but can lead to bigger issues
Sounds like you have a converter lock up OR line pressure issue
Have you tried scanning live data to see what the PCM is commanding and when?
Check for manufacture specific (trans) codes?
I build custom RBV, specializing in drivetrain conversions, wiring, suspension and complete custom trucks