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Tahoe & SuburbanThe power, space, and brutal towing ability make the Tahoe and its longer sibling, the Suburban, arguably the best full size SUV's on the market today.
In a perfect world you use a 6mm Allen wrench inserted vertically into the top of the adjuster and rotate easily (like they did at the factory). In the real world the bevel gears inside are dry and haven't moved in years. Conveniently there is a hex socket at the end of the adjuster assembly (oriented horizontally, on axis with the adjustment screw itself). It takes a larger 8mm Allen wrench. This gives you way more torque so be careful. I slowly worked mine left and right in small increments to free it up. After that the adjustment was easy. Note, the whole adjuster assembly will rotate if you don't hold it in place while using the large Allen (if it's stuck). This method allows you to skip the dual bevel gear arrangement and go straight to the source.
It takes more time to get access to the rear hex socket than anything else. Driver side is no problem if you don't have the dual batt. Passenger side takes time. Need to remove the plastic "upper radiator support cover", then the tubular brace located on top of the air box, then the air box itself. After that you're good. Btw, if you haven't removed the air box before, it's not bolted down. Once the lid is off you just pry it up. Start from the corner farthest from the fender and closest to the fire wall. Once that one pops, work the corner closest the radiator. After that you need to release the fender well snorkel from the airbox (two plastic tabs... they break easy).
The adjuster is marked "L" and "R" with an arrow. Not intuitive in my opinion but what it's telling you is... Rotating right (clockwise) will aim the beam down. Rotating left does the opposite. You don't need this. Just look at the beam on the wall.
For Reference... My '17 Suburban has a 3" front leveling kit. Measurement from ground to front wheel arch is 37". Measurement from ground to the crosshair on the headlight lens is 42". I parked 25' from wall on a level surface. Marked 40" on the wall for each light. Results are good.
Beam Height adjustment illustrated...
In a perfect world you use a 6mm Allen wrench inserted vertically into the top of the adjuster and rotate easily (like they did at the factory).
Uhhh - this is a GM, remember !!!
We have a 2014, and replacement of the headlight bulbs is not even covered in the owner's manual because fender liner, bunch of clips on top, etc., must be used for access. Took me like 45 minutes for first side, then maybe 30 for 2nd side a month later. Owner's manual says "take to the dealer".