[Thelocksmith66]

if you back up quickly you could cause your speedometer to reverse direction so instead of it being on 0 it will be on 200 and when you drive as you speed up the speed ometer goes down rather than increasing. Disconnect your power under hood at jump bolt wait several minutes. We waited 15. This reset speedo and it works.

 

[NickJ]

Sounds highly unlikely. I would suggest that you don't reverse quickly. "Quickly" is reserved for forward gears in the appropriate setting.