1998 GMC Adjust the Headlights
GMC boasts a sturdy line of pickup trucks. In 1998, GMC used a dual headlight system for its trucks. Should these headlights become off-center or angled, adjusting them is a priority as this creates an unsafe situation. The headlight assembly has two adjustment screws per headlight: a center bolt that controls vertical adjustment and one towards the side that controls the horizontal. Adjusting these bolts to realign your headlights is simple to do.
 Tools Used
 Adjust the Headlights
- Measure from the ground to the center of the low-beam headlight. Measure from the center of the low-beam headlight to the center of your vehicle's grille.
- Move the vehicle to a level surface with 25 feet of area in front of a wall or other flat surface.
- Mark the measurements on the wall or other surface with masking tape. Place a cross at the height of the headlight. This mark is the center point for the grille. From that point, make two more crosses for the driver and passenger's side headlights. Use the measurement from the center of the low-beam headlight to the center of the vehicle's grille to identify where to place the second and third crosses.
- Turn on the low-beams and adjust the headlights. The headlights will make circles on the wall or surface area in front of the truck. The top aspect of the circle should be flush or just below the horizontal lines on the tape and centered on the vertical lines. The high-beams should be centered on the cross. Vertical adjustment is done with the center adjustment screw, and left-to-right adjustment is done with the side adjustment screw.
 Tips & Warnings
- When in doubt, aim a little low and adjust towards the center-point of the vehicle. If you do not have an area large enough to adjust the lights, you can use a smaller area with the same measurements, but instead of making the horizontal adjustment flush with the line, make it slightly intersect the line but still be mostly beneath the line.