It's really hard to comment without actually hearing the noise. The best way
is to actually have a good technician riding in the car to hear it. But
these things can come and go, particularly at this time of year (if you have
winter weather where you live).

When you say they "lube the brake" I presume this means the calliper mount
(brakes themselves should always be clean of lubricant). This does not sound
dangerous, but there may be dirt lodged somewhere, or unusual wear in a pad
or rotor. The only way is to pull it apart and look.

I don't know who told you about a transmission mount, but that should make a
noise at various times, not just stopping.

The actual cause may be something quite different, some loose vibrating
item. There's been cases of weird noises that turned out to be a mechanic's
tool left under the hood.

Get yourself a calendar, even keep last years.  Write down the
symptoms, repairs, and dealer responses.    Keep thos calendars as
well as the repair reports.

If at one point you become very unsatified, then you might need this
information is the car is a lemon.

hth,

tom @ www.FindMeShelter.com

I have a 2003 ZX5 with a little over 40k miles on it and starting at the end
of December 04, I started having the same symptoms.
Almost non existant from first start-up, and slowly becomes more noticeable.
It sounds worse sitting still in reverse.  And it is worse after about 20-30
mile of driving. (My Guess it gets warmed up.)  Sounds a bit like a hammer
tapping on the underbody?
I suspect it might be the Transmission Mount Bushings??, but I haven't had
it up on a lift yet.
Dan