Please help!!!

[Travise90]

Today i was hauling some firewood and the engine was running fine then all of a sudden the RPM tac started jumping all over the place while the engine was maintaining it's current RPM. it would jump all the way from 1000 rpm to up to 3000 rpm but the engine stayed at it's current rpm's. and this is all under load climbing a short grade. There was some decrease in performance but not from the engine. After i arrived at my destination i let it cool down and on the way home it ran perfectly normal. Perfect performance. At first i thought it was the clutch but it never did it again and i have some steep grades going to my house. It's funny how the tac was jumping around but the engine stayed at it's current rpm's Could it be electrical maybe? I don't know. I would really appriciate the help. Truck has never given me problems. 2003 6.0l F250 130,000m i tow a 30 foot toy hauler from time to time and never had any problems with it before. Thanks Travis