converter shutter?

[MrJohnWayne]

Hey all. Got a problem with my buddies 04 6.0. pretty sure it is the converter shuttering. Will only do it in lower rpms after converter locks up especially in OD. can put it in tow haul and it will not do it as often as it doesn't lock the converter till higher rpms. cruising 70+ with the converter locked it doesn't shutter... Who makes a good aftermarket converter that will hold up to heavy loads and good tunes? Checked out ATS. Is there anything else out there?

thanks!

[Dave]

Suncoast or NADP