[daveinaz]

As has bee said, it is likely a hydraulic ram leaking past the internal piston. Had the same problem on mine and had to replace the main slideout cylinder. Since the slides are basicaly one big loop on the retract side, if fluid leaks past the piston when closed it can migrate to the extent side of other slides. Like yours, only the bottom of the slides extended. First the main slide about 6-8 inches. If I didn't stop and retract it, it then the creep would extend then to the bedroom slide 1-2 inches, and then the kitchen a little, etc. It's not a hard job to replace a cylinder, just a PITA to get to it.

Ours is also an old rig 2008 3400RL with all hydraulic slides.