To my untrained ear, I have a noise I would describe as that of a kid putting a playing card in the spokes of his bicycle. It started a few weeks ago and would come and go, sometimes loud, sometimes soft, sometimes not at all. Most of the time it is rythmic, but in the beginning it was sporatic and rythmic both. It is now all the time and fairly loud and there every time I turn the beast on. It does "speed up" when I accelerate, and sometimes is not rythmic (like this morning when I was coasting to a stop). I have 160K on it, just dropped a new Jasper Transmission into it. My current mechanic says he has never heard this sound and is only guessing at this point, what it could be...has checked and replaced the (?) tensioner belt, and now says maybe power steering pump?? Help....

 

Make a video of it put on youtube and post it here so the sound can be heard. IMO

 

99% chance is that you're exhaust manifolds are blowing - yes I know it doesn't seem the right sort of noise but on a D a clicking sound is the usual symptom

if it speeds up with the engine reving or and/or is worse when the engine is cold then make that 99.9% chance

often people think that there is a problem with the valve train as its coming from that area

you will have to take off the exhaust maifolds and then reseat them. problems include warped manifold that won't line up with the stud holes and also breaking studs off - very common i'm afraid

its metal to metal contact with the cylinder block although i believe that there are after market gaskets available

good luck...Chris

 

+1 on the exhaust manifold gaskets.


Also try a better octane of fuel or a different maker like Chevron. It could be a ping issue.