Abstract: A tensioner for an engine-driven chain applies a decreasing tensioning force to the chain as engine speed increases to suppress howling. The tensioning force is applied by a spring. The decrease in force is achieved by an expansible chamber in fluid communication with the engine lubrication system. As engine speed increases, lubricant pressure increases, causing the expansible chamber to apply a force to the tensioner which opposes the force tending to apply tension to the chain. In two embodiments described, a ratchet with backlash is used to prevent excessive slackening of the chain following sudden increases in chain tension. The backlash allows the lubricant pressure in the expansible chamber to decrease the force applied by the tensioner to the chain.