That's the pressure jacked up really high. You could ask him to adjust it lower.
I had my 518 rebuilt and told him I wanted a firmer first to second shift, he jacked up line psi and so my reverse makes a lil buzz noise and 1 st is a little noise..but it grabs second like no bodies business. He said it was built for holding power being it's a 4x4 truck.
Its not staving.
See how it drives 1st though.