A agree with Stumpy for starters and I'm guessing the clock spring in speedometer might be faulty and I'd replace or re-lube the speedometer cable. Also I'd pull the circuit board while in there and check all the sockets for good contact. The pinging I'm guessing is clock-spring. I see NOS Speedometers for those frequently on ebay if that turns out to be bad. IDK how much you'd be willing to spend though. They tend to be pricey.