Lifters ticking - fix it or sell the truck?

First confirm it really is a lifter. Quick checks to tell a lifter tick from something worse:

• Where it comes from: a lifter tick is up in the valve-cover area; rod knock is deep in the block or oil pan. A long screwdriver (tip on the valve cover, ear on the handle) or a mechanic's stethoscope helps.
• Cold vs hot: lifter ticks are often loudest on a cold start and fade as oil pressure comes up. Rod knock doesn't change much with temperature.
• Load: rod knock gets louder under load and with rpm. A lifter tick is usually most obvious at idle and may quiet down with rpm.
• Kill one cylinder at a time: if the noise drops out when one coil is unplugged, suspect that cylinder's rod bearing. A lifter tick keeps going because the valvetrain still moves.
• Rule out an exhaust leak: a leaking manifold gasket can sound just like a tick, especially cold. Look for soot at the ports.

If it is a lifter: start cheap — correct oil level, fresh oil and filter, and a look under the valve covers. If it persists, a failing lifter should be replaced before it damages the cam lobe it rides on or breaks apart. A lifter job means the heads come off on an LS, so it's real work, but it's a known repair.

If the truck has AFM (many GM trucks and SUVs from 2007 on — check yours): AFM lifters are a known weak spot. Typical signs are single-cylinder misfire, persistent tick, rough idle, low power, cylinder-specific misfire code; can progress to bent pushrods, cam lobe wear and metal in the oil. An AFM delete is a common fix, done often in the performance world — see what AFM is and whether to delete it.

If it's rod knock (deep knock, worse under load, oil pressure low), that almost always means a rebuild — factor that into the sell-or-fix decision.