Hill Descent Control Noises

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carsdad@gmail.com - 20 Oct 2006 16:01 GMT

I recently purchased a 2006 Frontier NISMO with Hill Descent Control
("helps control the trucks descent speed so the driver can
concentrate on steering"). 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. Anyone know about HDC? What's the deal with
the noise? I checked with a Nissan Truck Forum but nobody had any
clues, and I have little faith in the local dealership's knowledge.
Also, is there a use for this technology? Seems to me that a foot on
the break would work just as well.

Thanks in advance,
Chris J

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Mike Romain - 20 Oct 2006 16:46 GMT

The noise you describe sounds to me like a t-case not fully going into 4
low because the speed isn't right or the linkage isn't right.

Most 4 lows need to be engaged when either stopped or just rolling one
or two mph. If you try to put it into 4 low any faster it will make
noises like you describe.

When snow hits, I recommend you take your 4x4 to an empty parking lot
and learn how it handles. Using the brakes to slow down fast on some
snow or ice is a disaster. If you use the gears to come to a controlled
stop it usually is a shorter stop than using the brakes. A far more
controlled one too.

When descending in 4 low in snow, the gears are the way to go. If you
use the brakes, the wheels can lock up easily which slides you sideways
faster than you can blink.

On a 2 wheel drive when doing this, usually only the front wheels lock
up so you can't steer. In 4 low or 4 'part time', the front and rear
axles are locked together on most vehicles so if the front wheels lock
up from the brakes, so do the back ones. This leads to sliding to the
low side of the road or off the curve really quickly which puts a lot of
4x4's in the ditch.

The owners manuals for both of my Jeeps say to stay off the brakes when
in 4x4 trying to slow down and/or avoid something. It says to use the
gears.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
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> I recently purchased a 2006 Frontier NISMO with Hill Descent Control
> ("helps control the trucks descent speed so the driver can
[quoted text clipped - 17 lines]
> Thanks in advance,
> Chris J

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