Pretty sure it's not transmission issue
First gear is pretty solid but can't pull it in first, it wants to jump off dyno
It was a 3rd gear pull and it blows thru it, 4500 on dyno 6k on the car.
Not that I agree or disagree but this guy typically works on newer car tuned for Hennessy for 5 years , he said most newer cars have a button to lock up convert.
One thing was good fuel injection was spot on AFR was great.
I can tell you from being around modern power,added cars what I call high speed torque not all Dyno Operators are the same.
Thier predictions are often way off.
My 2nd 455 I had it on a,Superflow water brake dyno.
The 1st Full Pull with a Full Bore Comp Cams Racing Cam it made way more torque down low than predicted.
It was September 1997.
Good Old Ted Borowski was working the Dyno himself.
A Chevy Shop and they specialized in Big Chevys 900 -1400 Hp Normal Aspirated.
Jokes were cracked.
Ted was mocking me.
Engine running.
Thumping away.
He hit the Throttle WOT and worked the Dyno Brake by hand.
Was not computer automated back then.
The Engine Raced away and on the Tachometer it Read 9,000 RPMs on the huge 18 inch face tachometer.
Sounded Great but was not to exceed 6500 rpm I told him.
Ted shut my RAIV 455 down.
I looked at him and he got real nervous.
Valve covers pulled and checked the Valve lash myself.
No Tuilped stretched valves.
Valves did not float.
Best parts available used at the time.
Like I said you can not have HP without TORQUE.
Made around 20 more pulls and I tuned the ignition and SD455 Q-jet to get best results.