knocking

i have a 93 disco 3 door v8 manual just yesterday it started making a knocking noise when i pull up to a set of lights or other intersection,it starts not loud but audiable and tappers off its not constant it only does it for a couple of seconds and i can feel it through the gear stick, its not coming from the engine  more from the gear box ,transfer case or frount diff and sounds like when i pull up theres something still spinning in the drive train, holding the clutch in doesn`t seem to make any differance,the truck drives well and doesn`t do when i`m driving but there does seem to be a new noise in the frount end when i hit bumps which i havn`t been able to locate yet.any help with this would be greatly appriciated.thanx...

i`ve also notice a periodic vibration in the front end when i`m at speed around 110 klms and also when i`m gearing down to corner i`ve just put new tyres on all round and put it down to that but there street wheels without huge tread patterns so thats not the cause, it started  after i ran the a/c but that couldn`t be the cause could it possibly be that the truck isn`t fully out of 4wd or a low oil problem in the gear box or front diff?

sometimes the balance weight on the flywheel touches the starter head
this is due to thrust bearing wear on the crank bearings
i'm not an expert on standards living here in the u.s.
there very few discoverys that are stardards here
and half of the defenders are standards
try removing the access cover on the flywheel
and inspect the weight for scraping type wear
you may have to turn the crank bolt to see the
balance weight.

thanx raid i`ll have a look