Hi fairchasekennels, welcome to truckconversion.net! I believe Showhauler uses Liftco slides? There web site is Welcome to Liftco, Inc. - Liftco - RV Beds, Flush Floor Systems, RV Folding Beds, Glide Outs, Manual Roller Slideouts, RV Beds, Stabilizing Systems, and more!
. I just searched around there and can't find their advice about what to lube the threaded rod with. I just sent an email question to them asking about this. I've got a can of spray lube that I shoot up onto that road every once in awhile. I don't know if it's the best stuff to use though. I'll reply when I hear from them about their advice.
'03 Freightliner FL112, 295" wheel base, with '03 United Specialties 26' living quarters, single screw, Cat C12 430 h/p 1650 torque, Eaton 10speed , 3.42 rear axle ratio