The temperature gauge works fine for about 20 miles, then it pegs and the "Check Gauges" light comes on. I have replaced the Temperature sending unit. Stiill have the problem. Is there another component that could be causing this problem?

How about a bad thermostat sticking closed and actually causing it to overheat ? That would have been the first place i would have checked. It could also possibly be a waterpump going or a clogged rad, any of these will cause an overheat problem which is what you have, not a bad sensor i believe. Also you posted in the wrong forum, this is for 99 and up, you should be posting in the c&k forum for future reference. Good luck.

Sorry that I got into the wrong area. The truck doesn't overheat, just the gauge acting funny. I have talked to a guy at O'Reilly's. He said the gauge cluster would need to be replaced.

I have talked to a guy at O'Reilly's. He said the gauge cluster would need to be replaced.

or you could have gotten a bad sending unit or even the wrong one. if your oreill'y is anything like ours they go through help faster than mcdonalds if it is bothering you go to a shop and get it checked out most parts guys these days haven't got a clue