Mike, without knowing the exact brand of slide system you have, from your description it sounds like a PowerGear motor unit. These make a distinctive ratcheting sound when the load is excessive and/or reaching the full in or out position (travel) of the slide room. In this type of system there are no limits on travel, the motor will continue to run as long as you're holding the button down. The gearbox is designed to create X amount of torque - once exceeded, such as reaching the slide room's full in or out, it "clutches" to prevent damaging itself, which is the sound you're hearing. This is all perfectly normal.
If the slide room is out of alignment badly, needs lubricated or perhaps has something else wrong causing excessive difficulty in closing/opening you'll hear that ratcheting sound as it's traveling - It's telling you something is wrong. Also, Broken shear pins are, in many cases, a sign of something else wrong.
The room needs inspected and run manually to see if something is indeed hanging up somewhere. It is entirely possible that the room is just fine and the gear unit on the motor is wearing out. Fortunately, these motor units are quick and easy to change.
94-Newmar Kountry Star 40-KSDP
Spartan/Cummins 8.3C-300HP/Allison 3060 WTEC-II/25yr RV Tech RVIA Certified/Onan-Cummins Certified