Ticking noise in Audio Research Reference CD7


Hi,
I have a relatively new CD7 (probably with about 1,500 hours on it) and it recently started making this ticking noise each time I press "play" or move between tracks ("forward" or "backward"). While just playing the noise isn't there.

Any ideas where this noise could be coming from/caused by?

Thanks.
amuseb
Sled motor.
The rails may just need a little lubrication.
Actually you can open up the unit and move the overgrease already in there back onto the rails for free.
Usually it is a white grease in lumps at the end of the rails. Just spread it around back on the rails with a toothpick. Don't waste it, just use half of it. leave the rest for next time.
Hi Elizabeth, I've opened the unit but can't see the rails. Do I have to also lift the CD tray to access those?
Is there anywhere where this process is described with pics for my layman self?
Also, I live in a very big city and there's a lot of dust/dirt/smog in the air at all times. How do you clean the guts of those units (CD 7, Ref 5, etc) that have practically no protection from all that dirt?
Thanks.