1998 Mercury Mountaineer Clunking noise

Hello,

You might have those noise coming from the front axle shaft.

First visually inspect the shaft for any damage, loose bolt etc.
Check the CV shaft, make sure that the boot are not leaking.
If the boot leaks than all the grease will escape and it will make clunking noise when you drive.

Here is a helpful article:

https://www.2carpros.com/articles/clicking-sound
https://www.2carpros.com/articles/popping-noise

Also check your lower ball joints for excessive play.

I have attached diagrams for your reference.

Please let me know of any questions.

Thank you.