What can it be

My P38 has just come up with a new problem can anyone give me some idea what it might be. The problem is when i slow down but not using the brakes the car feels like it is going over a cobble stone road. I have no problem at speed or excelerating. She is an automatic and i have rolled her down a road in nuetral and still feel a slight rumble.

Prop UJ's?

Thanks i wil get it checked.

front suspension bushes are also common thats what my neighbours one does and he was quoted hundreds to replace them (special tool needed)

were they planning to give him the tool afterwards??

Had it checked it is the prop shaft UJs that are past it so thanks you guys.