Strange shaking and ticking while going down the highway?

[explorer_redneck]

right around 55-60 mph, i get a strange, violent shaking and a large power loss, also associated with a low end ticking.. only way to correct this is by giving it about 3500 rpms and speeding up. not sure what it is, any help is greatly appreciated! 92 ex 4.0L A4LD