Sorry for the confusion on my part. I believe that the LTs use projector headlamps. This system uses the same bulb for the low beam and high beam.
Each headlamp has a "shutter" that chops off the top of the high beam to create a low beam. This can be easily seen when operating the lamps.....there is a visible light cutoff visible in the distance. If one or both of the shutters fails to operate the projector will stay on high beam. You can lift the hood and listen for the shutter sound. From what you describe could be a frozen shutte on one of the projector assemblies.
Current Chevys -'16 Silverado LT;'18 Malibu LT Redline;'18 Traverse Premier Redline<br /><br />Previous Chevys:16 Malibu LT2 '17 Impala;'16 MalibuLT;'15 Camaro LS;'15 Traverse; '13,'12 and '07 Avalanche LTs; '11 Tahoe LT; '13 &'11 Malibu LTs; '08 Trailblazer;'06 Colorado WT..... Chrysler era.....'80 Citation;'75 Impala;'72 Chevelle;'69 Camaro R/T;'65 Impala SS;'62 Nova