4l65e slips

[BLeeBull]

Ok here it is. My transmission or converter clutch slips during light throttle steady state cruise. If I am rolling along at about 50 mph/2000rpm in overdrive and I slightly apply throttle (15-30%) the RPM flairs up like something is slipping. If I give it even more throttle (35-50%) it locks up hard and quits "slipping" the rpm drops a few hundred and feels more like a standard transmission up to and until I give enough throttle to downshift into 3rd. 1996 c1500, LQ9, 4L65, 3400 converter, "built" tranny, 4.10 gears, 28"tire, DBW, TBSS intake, 90mm TB, 220/226 cam, 1 3/4 longs with 3" . It feels locked up unless I am really light throttle, like the more throttle the more direct drive it feels. Should I lean more toward looking for an internal trans problem or does it look more like programming? If it were a 700r4, something I owned many of , I would blame it on a loose TV cable because that is how it acts. Weird sensation for the trans to suddenly lock hard and drop rpm as more throttle is applied while stayingin the same gear. I paid somebody for it to be tuned after I put it together, never drove truck before tune, always acted this way. I am not confused by a loose converter. This is A really mild 400 ish hp maybe.

[mach]

maybe datalog TCC slip and see if its the clutch slipping , or trans itself