1998 Isuzu MU 3.0

[local4x4guy]

Hi there I'm just wondering if any one else has ever come across this,

my MU drives fine and does everything that its meant to do,

However when I'm doing 100kms an hour just cruzing along and if i
go to overtake someone if i put my foot down i get this weird loud
clicking noise and it sound like its coming from my left hand side of
the engine, it only does it when its about to hit 4thou revs. and it
does it if i put my foot down to get up and over mountains