Could be messed up speedo or could be messed up speedo cable.  Check where the
cable end sticks through the center cap of your front driver's side wheel.
See if the little metal round clip is still attached to the square end of the
cable.  If not your cable could be slipping a little and causing your
"jigger".
I sell speedo cable if you need one.
Ken Wilford
Van-Again
John 3:16