Torque Converter, Tranny, PO770 Problems

So, i know there are tons of threads about PO770 for all Toyota and believe me I have read them all. Mine is doing things a little different. Please help if you can!

I have an '01 quad cab and since i got it 3 years ago it has set the PO770 randomly. Like everyone else, it doea not affect drivability. TCC lock up occurs at 45 MPH and I watch/here it happen. That being said, The tranny shifts from park to drive OR reverse/ reverse to drive/ drive to reverse HARD! The truck lundges whichever way and the gear hits hard. This happens 98% of the time and every now and again it is soft and smooth. The truck runs through the gears smoothly accelerating and down shifting.

I do not know if it had a shift kit installed or if there is one even available for it. My thoughts lay with the torque converter or a possible shift kit. I dont know how I can tell if it does have a shift or not. Any help or insight would be greatly appreciated.

Thank you