I read a few years ago that the dealers disconect the odometers on the 99 and up trucks as soon as they came into the dealership on trade so that they can drive them around for their own use and not put on any miles on. I told this to a friend of mine who works at a dealership and he did not believe me. Did anyone ever hear of this ,and do you know how they did it ?

I would say not likely. The risk of fines/penalties (jail time) isn't worth the minor price difference they would receive in reselling with a few more miles on it. Not to say there is not some less than reputable dealers out there, but for most it is not worht the effort.

I would agree. This may have been a practice 20+ years ago, but these days it is not as common.

I've also heard from a few sources (GM Engineers here in Pontiac) that the 99+ GM trucks track mileage in the cluster as well as in the trucks computer.

Years ago vans and trucks where taken home regularly by management (for quality purposes) from the assembly plant. One morning they were all stopped by law enforcement. Its a federal law to disconnect the odometer. They completely quit the practice. I'm not say its not done but thats what happened here.

I would agree. This may have been a practice 20+ years ago, but these days it is not as common.

I've also heard from a few sources (GM Engineers here in Pontiac) that the 99+ GM trucks track mileage in the cluster as well as in the trucks computer.

The ECM tracks the mileage and it gets it off the VSS which is where the odometer gets it also. I can't say for 100% certain, but disconnecting the speedo only disables the speedo. The odo gets it from the ECM. I haven't tested this buy on the 2000 Silverado we have a turbo on, HP-Tune displays the mileage from the ECM.

Only way to do it would be to disconnect the VSS, which would then create a whole mess of issues, such as ABS, cruise control, fuel mileage, transmission, etc. to not be right... Its not really feasible on a newer Chevy to do it without something really going screwy. Biggest thing is the transmission relies on the VSS to detect slippage, shift points, time it took to shift, effective gear ratios etc. unhooking one will likely make the vehicle default to second gear along with alot of other issues (never tried it but I think a VSS issue will cause a second gear default)

You can disconnect one wire from the back of the instrument cluster and it will trip a code in the BCM and check engine lamp will come on but it is a hassle to do since you have to remove the entire cluster but it can be done. I highly do not recommend that you tamper with mileage as they take this very serious these days. These trucks have hour meters on them too now that you can not tamper with.