i hear a grinding, not scraping sound coming from the bottom of my truck. It makes this sound when driving, turning, breaking..but not when cranked. I feel it from the bottom of the truc, when drivin.

theres a possibility it could be the loose cable from the transmission that goes from the handle to the transmission

Thanx, we'll try :-)

Thr rear wheel seal ia leaking, could that be related to this grinding problem?

Yes it is related to the problem but its not the problem. The problem is the rear axle bearings are bad causing the grinding noise from no oil to lubricate the bearings because it has all leaked out.

Check the exhaust.