help with dampness after towing

First trailer I had did that. Very poor build job on the seal under the slide. Dealer did a sloppy fix, but was better. Present trailer manufacture knew how to build a slide seal. Tighter than a submarine.

I found my carpet soaked by the slideout after towing in a rain a year after I bought it. it turns out the tires were directly below the slideout seal and the water was spraying up into the trailer (seal was good, it just couldn`t seal against a pressure wash type spray!). I bought some galvanized sheet metal to make a shield to keep the water from spraying up into the trailer. In the 8 years since the carpet has been dry after towing in the rain.

Yep, check the seals, especially underneath where the wheel well is. You may have mud or some other debris making a gap in the seal. Or it could very well be torn and need to be replaced. Then again, might the slide need adjustment so it fits evenly along the side of the trailer? Diligence is key in the fight against water intrusion.

Maybe another question would be how much might it cost to have the rubber seals all replaced?

That's a start. It's actually at the back end of the slide out? Possibly spray up from the wheels? It that at all possible?

I would play a hose on the leading edge of the slide as you obviously have a gap in the seal somewhere. Vacuum with in the rig would help pull this in. It may be a little hard to find, and seal, but anything can be done. I might also investigate putting a slight shield in fron of the forward edge of the slide to deflect water and air. Something akin to the air deflectors used on floor ducts on heat and cool systems only longer.