One problem related to transmission fluid leaking has been reported for the 1999 GMC Sierra. The most recently reported issues are listed below.
Brake fluid leaking all over bottom of truck spraying out I took to a mechanic and had 1000 dollar brake line job done got truck back and abs brakes worked like manual brakes had a sensor and 2 ball joints replaced im being ripped of from a GMC loyal customer I was I guess back to Ford or Toyota for my next new trucks I had warranty issues you cheap [xxx] wouldnt pay for a waterpump that was leaking only a 7 dollar gasket also had a transmission on my work van repair and then replaced after a month of run around. Information redacted pursuant to the freedom of information act (foia), 5 u. S. C. 552(b)(6).