Hi,

When the TC locks up it is super quick and hard, makes a loud bam, slam, boom whatever you want to call it. If I feather back the throttle just before it locks this softens it up.

Any thoughts as to why? Tranny fluid appears good, truck has 150k and most everything else works fine.

There also is a bit of drivetrain slop between power and coasting, driveshafts, joints and diffs are tight. Can a worn t case cause this?

I also have the harmonic vibration that appears after lockup like a few others have posted about. I doubt its related but seems to be getting more prevalent as time goes. ****, all kinds of issues I didn't realize till writing this.