Why is my truck started knocking and pinging? ?

The pinging and knocking sound often occurs when the air-fuel mixture is incorrect, which causes the fuel to burn in uneven pockets rather than uniform bursts. 

If you put in fuel with an octane rating too low for your vehicle, it can create a knock. ... The combustion causes the “knocking” or “pinging” sound you hear. To prevent this from happening, use gasoline with an octane fuel rating at or above what the manufacturer recommends.

Check for trouble codes with a scanner. 

Bad gasoline?

The ignition timing has changed?

Clues may be present in the codes. EGR clogged, carbon build up on piston. Bad gas. 

A condition causing the gas to pre-ignite has occurred. Any codes? Tune-up? Other factors?

Have you ever checked the oil level? 

English Lesson:  It should be "Why did my truck start knocking and pinging?"

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FAIL

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Answer: We don't know. Not enough information provided. WHEN is it doing that? Always? Only under hard acceleration? Going up hill? When the engine is warmed up, or when cold? Intelligent questions involve giving useful information. 

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FAIL

how are we supposed to know? Take it to the junkyard its a pos anyway.