Hey I just read this in a thread where this modelís slide mechanism was full of rust, horrible looking, and this is what was recommended.
Originally Posted by redjet
The rust on your slide gear packs looks familiar. We spend the winter months at the Texas coast and without maintenance any exposed or poorly painted metal will rust. Ask me how I know. Anyway after we got our 2016 Cardinal we had it undercoated as soon as we got to the coast. In addition, it is a must to lube all of the gear packs and along the under edges of the geared arms on the slide every couple of weeks, when in a salt air environment. LCi recommends: CRC Power Lube, High Performance Lubricant w/PTFE. The auto parts stores don't seem to carry it but we found it on Amazon. During 2017 FROG Goshen Rally, an LCi tech sprayed all of the gear packs on the fifth wheel, as they squeaked bring slides in and out. When he was done, absolute no noises and smooth operation.
This will not fix your current problem, however, the rust and lack of lubrication on the gear packs could cause some resistance during the slides movement. Just a suggestion - good luck.
We have one of these also and the slide runs fine but moans and groans, I want to do anything to keep it happy. I donít know anything about getting it under coated.