Shudders starting after 40mph
Hi guys
My crown Vic was driving just fine until mid day when it suddenly started shuddering after 40mph. It lessens around 80+ mph but resumes once u decelerate. I can hear a clunking noise in the rear when u decelerate too. What do you guys think this could be? All tires seem okay, no balancing issues. The CEL came on after awhile too, I feel reduced performance from the transmission.