2004 GMC Yukon XL Speedometer Problem

My speedometer registers from 50 to 100mph at idle and continues on up as the vehicle starts moving. Is this an expensive fix? Any ideas on what is causing this?
Thanks,
Mo
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This is the very common stepper motor failure endemic to virtually all full size GM/Chev/Cadillac SUV's and trucks from the 03-04 model year. Cluster replacement is the cure. There is a special extended warranty replacement for the cluster for 7 years/ 70,000 miles on all '03-04 units. My '04 Avalanche had it's replaced early last year free of charge. Your dealer will know this. I got a letter from GM Canada. http://www.gm-trucks.com/forums/index.php?showtopicp134
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expensive. Simply replace the stepper motor. Should be able to find new ones on ebay for $5-10. Easy to replace and instructions are easily found on the net. Make sure you get the revised stepper or you will have the same problem in the future. Your old stepper should be X15 168. Do a eBay search for X25 168, the revised motor. I would change all the stepper motors to the new style while I was at it, sooner or later the rest will fail.
Here is a example of a quick search http://cgi.ebay.com/ebaymotors/6-03-04-05-CHEVY-TAHOE-X25-168-CLUSTER-STEPPER-MOTORS_W0QQcmdZViewItemQQ_trkparmsZ72Q3a1205Q7c66Q3a2Q7c65Q3a12Q7c39Q3a1Q7c240Q3a1318QQ_trksidZp3286Q2ec0Q2em14QQhashZitem350125166326QQitemZ350125166326QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories
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Since this is 100% covered by GM warranty up to 7 years/70,000 miles and dealers will do the job past that point on a goodwill program, pulling the cluster yourself and replacing the stepper motor yourself hardly seems necessary.
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the OP's vehicle is covered under warranty of course get it fixed at the dealer but if not DON"T buy a new cluster.
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