4 wheel drive on 2001 Ford Explorer

When I engauge the 4 wheel drive I get a clunking noise every 30-45 seconds. The 4 wheel drive is engaged and working but it I feel this clunking every 30-45 seconds.

Asked by for the 2001 Ford Explorer
Hello,
Sorry to see you didn't get some help with this. Were you able to figure out the problem with the transfer case?
Bret
1 more answer
Have a 4 wheel drive explorer .where would I find the sencer for the 4 wheel drive