I have a 1997 Explorer 400 4x4. Every now and then I get what seems
to be a drive line noise. It can appear when travelling fast or slow.
It seems to cycle about once or twice a second, depending on speed.
I have always kept the machine well greased. I guess the biggest problem is that this "noise" comes and goes. It seems to be related
to the front drive as I seem to be able to feel it through the
handlebars when turning. Has anyone had this experience ? If so,
what is the problem/solution ?

 

check your universal joints. mine done that and that was what is was.

 

I do not know about an explorer exactly,but it could also be wheel bearings.UJ's are a good possibility

 

start by checking your sprockets (6), replace your sprockets, chains, lube them well with OIL, check the outer support bearing on the transmission output shaft.

 

take it to the dealer and tell him to fix the darn thing right, save you some headachs and keep the economy going