clunk or a click?
if it makes a click i would say for sure that the solenoids are on there way out....
However i would advise first of a bit of routine maintainence & clean & grease all the connections (power & earth leads) first & go from there
if you can remove the solenoid box cover & check to see if it has the "can" type solenoids, if so these are crap, remove the soleoids & replace with either a genuine allbrite from Devon 4x4 (
www.devon4x4.com) or a superwinch Hd solenoid from Gwyn lewis 4x4 (
www.gwynlewis4x4.co.uk), the superwinch solenoids looks similar to the allbrite but is a bit cheaper, i have both types on my car & can vouch for them being pretty good