That's a pretty vague question without knowing where you hear this, engine area, trans. area, rear end area, inside the car? On this forum that I belong to there is a person who loves these kind of questions and his answer would probably be,"TEACH IT TO SING THEN".
Typical U-Joint noise. Makes noise in reverse but not in drive. Check both front and rear U-joints of the drive shaft. If one is bad replace both. You do not want to go through R&R of the drive shaft twice.
age
Bad shock mount? Loose exhaust system?
No
go to markviii.org. they have a answer for almost anything with the lincoln mark viii
There could be a problem in the steering linkage but most likely, the power steering pump is bad or low in fluid
Where to find the horn relay fuse for a 93 Lincoln Mark VIII
no
You didn't mention whether you hear it all the time or just on startup? If on startup, the timing chain has a tendancy of making noise especially when cold. Usually the lifters don't make noise in these cars unless the oil is really dirty or oil level really low.
Not unless you try to change the whole front end of the car.
Check the basics, With an inline spark tester ($6-8.00) check for spark. Does the fuel pump make noise when you turn the key (whining noise)? Is the fuel getting to the engine?
No way