I have a L77 6.0 w/6l80 out of 2017 Caprice police car with 20k miles on it swapped into a 56 Chevy. I put a trans tune out of the Tuning School trans guide. Car seems to shift better than before (It shifted very soft before) , but at WOT it won't go in gear. It sounds like it bounces off a rev limiter at 6000. I raised rev limiter to 6500 and lowered the WOT shift to 5500 rpm to see if would shift, but it still cuts out at 6000rpm and won't go into gear until I lift off throttle. Put a scan on it and I noticed the trans output shaft reads 0 rpm. Does that mean the sensor would be bad? Doesn't have very many miles on it. I'm new to this so I just want to make sure I'm not missing something on the tuning side before I go and pull the valve body to change the sensor. Any advice would be appreciated.