[JeEpBoY95]

i had the same prob. my t-case got low on fluid and got so hot that is melted the speedo drive gear....it is located on the rear half of the t-case near the top. it takes a 1/2in wrench to remove and as soon as it comes out you will be able to see if that is the prob. if that doesnt help then it is probably your speedo cable which you can test by removing and spinning with a drill to see if it will spin.