Our Mazda has a vibration and noise that starts at speeds greater than 40mph. If we let off the gas, it smoothed out and the noise/vibration stopped. When we accererate, it starts up. It it continuous (unless we let off the gas). Last week, we drove it about 230 miles for a family emergency and were on our way home (the next day) when the noise and vibration got MUCH worse. Normally, we only use it for driving close to home. It is currently 'in a shop'; they said it is the universal, but that we need to replace the entire driveshaft. Our son owned the car before us and suggested that I ask via a Mazda forum (that's where he always went for information when he had it). Any thoughts?

 

It odes sond like a drivesahfrt Universal joint problem.
Mazda did make the Shaft with "unreplacable U-jpints" ..BUT they can be replaced at a competent driveshaft shop.
There should be some Threads on here with a bit of info if you can you use the search feature.