[JFCalvano]

For what it's worth: About 2 years ago my 2005 Chevy Tahoe was having the exact symptoms described by "cory e" earlier in this post - warning messages about servicing the 4x4 system which resulted in having the dealer replace the cluster of 4x4 switches in the dash. Problem solved (for a while).
Today (after experiencing the other symptoms that 'cory e' mentions exactly,... stability control and 4x4) my 2005 Chevy Tahoe is going to have its Encoder Motor Sensor changed out at $452.02 (which I assume now is only the part).
Thank you Cory E!