Speedometer

[ajj08120]

Hi, Recently my speedometer has been acting wacko…and continues to do so. Two to five minutes into a trip it will slowly increase or decrease in mph’s and randomly stop (or continue) as it pleases regardless of how fast or slow I am traveling. Several mechanics checked it and test drove it and no one could figure it out. The devices they used to check the speedometer indicated it was functioning properly. Two mechanics suggested asking car talk as someone may have come across this dilemma and may suggest a solution. So, here I am. Thank you for your time.