Four problems related to seat broken have been reported for the 1999 GMC Sierra. The most recently reported issues are listed below.
I have a 1999 GMC Sierra extended cad truck the drivers seat adjustment made of plastic when it breaks the seat will not lock. The seat belt is attached to the seat so in the event of an accident all that is holding is flimsy plastic. I checked all the salvage yards in my area they said every truck that they have that has wrecked the plastic slide is broken. To me, my wife and my life are worth more than this plastic piece. Gm needs to recall and either fix this piece with metal or different seat tracks. My seat broke just adjusting it.
As I was driving down the highway I had to apply my brakes very quickly and a part in the manual adjusted drivers seat broke and the seat slid forward pushing me against the steering wheel. After this incident the seat will not lock in any position (it slides free in the track). I reported this to gm and they equated it with brakes wearing out. I am so very thankful to the lord that nothing was coming because when the seat malfunctioned my ability to steer and continue braking was affected.
Driver's side seat track broke without force, driver was unable to position the seat. Cause unknown.
When attempting to reposition driver's seat, the seat would not lock in any position. After examing the seat consumer found a small white plastic rectangle under the seat. The seat was broken and consumer drove with the seat sliding back and forth.