speedometer failing

Since the car had 60k miles to speedometer started to freak out on my Rodeo 1999. It works sometimes and than suddenly drops to 20mph where it stays. When idling and using my indicator the needle of the speedometer is jumping a bit.

Anybody had this problem. Will ISUZU fix this for free?

Thanks
Steven

faer not
it is only the speedo pinion remove the speed sensor from the transmission there is a plastic gear in there it is worn not sure of the price but all you will need to replace this is a 1/4 in drive ratchet a10mm socket and a maybe about a six in extension oh oand the new part