Tapping noise at speed

[dropnosky]

1984 300D turbo, (subject of many posts from me). Here is the situation, at relatively heavy load, cruising at between 50-75, there is this disconcerting tapping noise, sounds like a valve train noise, but it is random, and inconsistent. I have not adjusted the valves yet on this car, and, it being really rough right now after the purchase, it could be anything.
I am trying to isolate the noise by fixing other things that could be masking it, (broken flex pipe on exhaust) but if I had a tapping valve noise, when would I hear it? the vehicle idles like a champion, and will not make the noise around town, but occasionally at higher RPM and every now and then on the highway. I would be less concerned, but it really sounds like an internal metallic noise, not a loose bracket or something. the oil pressure and power are excellent. anyone had a similar experience?

[cervan]

your absolutely sure its only at speed. not just at idle if its the engine it should do it all the time but if its only at speed it could be anything from the flywheel to the rear tires. most likely its something from the flexdisc that frayed and is hitting the undercarrage.

[dropnosky]

found it! not even close to an engine problem thank god.

I was chasing down some electrical shorts related to the power windows and radio, and had the whole dash apart. during this little operation, I drove the car down the street to get some electrical tape, and the antenna lead, (which was disconnected) actually vibrates and taps against a bracket deep inside the dash where it was stuffed. It sounds just like a valve noise, even while I watching it. That is a load off of my mind