One problem related to transmission shudder has been reported for the 1999 GMC Sierra. The most recently reported issues are listed below.
While attempting a three point turn across a road the automatic transmission began grinding after putting the vechile in reverse. I was in the lane facing oncoming traffic when this occurred. The reverse gear no longer functioned. Fortunetly there was no oncoming traffic and I was able to put the vechile in drive and straighten it out, getting back to the parking lane. The vecile only has 49,000 miles. In the research I have done on the problem so far I have discovered that the automatic transmission failing is a common problem. For example, a man named chuck who works at all-world transmission (262-547-0136) says these vechiles come in all the time with the same trasnmission problem. GMC claims it is a not a safety issue and will not issue a recall. I beg to differ. I had my wife and 5 month old daughter in the truck. If there had been a car coming, I might have been in trouble.