2017 Silvarado. LT4 swap, Ported heads, cam, Magnuson 2300, Yank PT2800 3 disc. Truck originaly came with a 5.3/6l80. We had the 6l80 built. The TCC will not hold 800 whp at 110 psi of TCC pressure. I had 200 rpm of slip at 7000 rpm. It also varies the pressure up and down at cruise and at light throttle lockup causing the rpm to surge up and down. Seems to want at least 40 psi to hold at part throttle cruise and light accel. When locking it wil vary up and down 30-60 psi 3 or 4 times before it settles in at 50psi and holds. if you move the throttle even just 2% the pressure drops to 30 psi the engine flares, pressure jumps back up to 50 and it holds. In the past I have solved this on the 6l90's by full flashing a Camaro SS 6l80 OS into the tcm. Will trying a older OS in this 2017 T43 brick it? Still has the original E92 ecu.