I recently purchased a 2006 Frontier NISMO with Hill Descent Control. According to the manual, the truck has to be in 4LO and traveling slower than 21 mph when HDC is activated. I followed these directions and slowly eased down a steep hill in my neighborhood, as a test. Suddenly, there came a horrible grinding and clicking noise from beneath the truck then, as quickly as it came, it stopped, and the truck chugged down the hill at a slow and steady pace, as advertised. But then again, the nasty noise came back for a moment then stopped, and we continued down.

I’m not familiar with this HDC stuff so I can’t say if this is normal, but it really sounds as though something unpleasant is happening under the truck. Any know about HDC? What's the deal with the noise?

Thanks in advance,
Chris J