DAC (Downhill Assist Control) question

I will apologize in advance if this is already addressed in the forum, I spent 30 minutes looking and didn't find anything specific to my question. So, here it goes... I have an 09 TRD DC (off road) and I tried my DAC for the first time over the weekend. When it was engaged and in 4 low, I began to go down a hill and it made all sorts of noise. Sounded like the antilock brakes were engaging (hard) and it would catch (with the noise) then release and so on as it was decending down the grade. Is this normal operation for this or do I have a problem? Thanks

 

I don't have it, but from what I have been told, that is normal. It clicks alot and actuates the brakes to control it.