Speedometer only works up to 40 mile an hour cruise control still

What is your question?

If you floor it the speedometer will jump back down to zero then when you let up it'll come back up to 40 mile an hour the speedometer is correct from 0 to 40 mile an hour

What makes this problem better or worse?

N/A

How long has your 2000 Ford F-350 Super Duty had this problem?

Just bought truck