I have a 1999 exp and it's been making a clunking sound when you are going any speed and get on the gas to pass someone also noticed it when pulling my camper and going up a hill or getting on the highway. It sounded like it was coming from the transfer case / front drive shaft area. I took off the front drive shaft to see if the u joints were bad but they seem fine. I took fuse 104 out and drove it with out the front drive shaft and no clunking. Already replaced cv axles and wheel bearings seem fine. Not sure where it is coming from. Either front differential or transfer case. With the front drive shaft in it was driving fine just when you got on the gas.