On a chassis dyno with an auto trans, you can only get WOT readings as low as the whatever the converter stalls.

For example, If you had a converter that stalled 3500...... that’s as low of a rpm that you could apply full power to.

This can be one of the reasons a power curve on a chassis dyno might not look anything like the same motors power curve fron an engine dyno.

If you have 4500 stall, but the motor actually makes peak tq at 3800....... on the chassis dyno the peak tq would be at the beginning of the pull, at 4500.