I HAVE A 2000 GMC SONOMA AUTOMATIC TRANS
ALL GEARS SHIFT FINE EXCEPT IT WILL NOT SHIFT INTO OVERDRIVE, 1- 2 -3 ALL SMOOTH , BUT THATS AS FAR AS IT GOES WILL NOT GO INTO OVER DRIVE, EVEN IF I MANUAL SHIFT IT JUST STAYS IN 3RD.
any ideas

Welcome to AF, please do not use caps. A full scan with a trans function scanner can see what is happening and whether this is a solenoid problem or an internal issue.