Nissan Terrano Leaks & Noises Problems

When i drive in 2 wheel drive i get a whizzing sound coming from n/s front wheel. It then starts banging as though trying to go into 4 wheel drive. If i then select 4 wheel drive and put it back into 2 wheel drive its ok. If i stop or rever...

after a while driving in 2 wheel drive, when i come to a stop it makes a clunking noise from gearbox