Erratic speedometer

That's hard to say because there are more than just the speedo unit involved in the functioning of the speedo. I believe it gets it's signal from the computer which gets it's dsignal from the vehicle speed sensor(s). The best idea is to take it to a Chrysler or Jeep specialist for diagnosis and an estimate. If you want to find a specialist, here's a directory link for you: https://repairpal.com/jeep-repair-in-warrendale-pennsylvania