Trying to diagnose a noise only when Engine is under Load. Light "Tinging" Noise which sounds like a Valve with excessive  clearance-but its not Engine. Fordomatic. When in Park the noise is not there. Put it in drive and start moving and the "Tinging" starts and increases as the Car moves faster. Tails off at about 30 or so or at least I can't hear it. Thinking maybe the Flex Plate is going.  Would I be able to see problem with Flexplate with lower Inspection Cover off? What am I looking for? What happens to Flexplate when it starts to go? 

  

I would ck the  "U" joints,  the flex plates can crack, but they usually sound more like a knock in my experience, and they are sometimes more pronounced going in one direction  ( drive rather than reverse, or the other way around .  cracks in flex plates can be difficult to see.

I just replaced my flex plate on my 56 merc, what you described is exactly what I experienced, would knock only in gear, put in park or neutral knock went away. Found that the flex plate rivet holes were rounded out. Ended having the transmission completely rebuilt, all the clutch plates and bands were worn, the car has 91,000 miles on it, I guess it was due. Works great now. The best deal on flex plate is Macs. 

I am checking the Rear Main Seal that I changed a couple of Weeks ago ( which seems to be dry)  and also having a look at the Flex Plate while I am under the Car. I can't see anything wrong with the riveted Brackets that hold the Torque Convertor but only the One side is visible. Where do the Rivets usually start to come loose? Is it the Holes in the Brackets that start to enlarge allowing the Bracket to come loose? On the side between the Torque Convertor and Flex Plate where I cannot see ?  I have ordered a new Flex Plate and I am going to install the Water Cooled Fordomatic I bought a couple of Years ago at the same Time..

  

Mine was the holes in the flex plate became enlarged, couldn't tell without removing, there was very little movement. 

Thanks John. I guess I will find out when I change the Transmission and Flex Plate. It seems to be a fairly regular problem. When they make new replacements with better Design it's usually a good indicator of demand. I see One Seller on Ebay with an Original that he has priced far higher than the new Replacements. Hope somebody doesn't buy it not realizing new better Replacements are available.

  

I had the same experience with my 1956 Victoria with Fordomatic over ten years ago.  This car was built in early 1956 (March) and had the air cooled Fordomatic and the flex plate with riveted ears.  I recall I couldn't see anything wrong with the ears by just looking.  After I got things apart it was obvious that they were loose. I replaced the early flex plate with the later one piece flexplate - after rebuilding the whole transmission while things were apart. It had crud everywhere that needed cleaning out and needed new bushings, clutches, and bands.  No problems since. 

Thanks for the Info. My 56 was early build Nov/55 and has the Air Cooled Fordomatic also. Changed the worn out early Steering Box to the later Style and now I am going to put in the later Water cooled Fordomatic.