Drivetrain Rattle

[Daniel R]

I have been hunting down a persistent rattle for some time now. It generally happens when coming off the clutch and accelerating from a standstill. It is much more pronounced when starting uphill, the car actually sounds terminally ill for a few seconds.

To give some background, it always felt like a drivetrain issue and I assumed it was a clutch and/or flywheel on it's last legs, possibly with loose clutch bolts as this is what it sounded like to me. I had those replaced with a LWFW and sprung clutch, no change at all to the rattle, some new vibrations due to the single mass unit but I was prepared for that.

The next suspect was a pulley or tensioner. The water pump was only a few months old and the rattle predated its replacement so not that. I replaced the entire alternator as the clutch in the pulley was not working as it should and while we were in there... At the same time all the other pulleys and tensioners were inspected and everything was working as it should.

Exhaust rattle? Seriously doubt it since I have no cats at all (ROW setup only has one set of O2 sensors post cats so no CEL) and I have replaced the engine and transmission mounts with semi solids so I doubt that the engine is torquing enough to move much of the exhaust.

Now that we have most all of the red herrings out of the way, what could be causing this rattle? Some slack in the drivetrain somewhere is what it sounds like to me. Where should I start looking? Is there a big bolt labeled "Tighten Here To Stop Rattle" type solution or is this another difficult case?

All suggestions are much appreciated.