I'm the original poster in this thread. To tie a ribbon around my problem, my buddy and I spent an afternoon tracking down the two squeaks buried in my dash somewhere in the corners (see pics in 1st post) where the dash meets the sidewalls. My buddy literally laid on the dash while I was driving down some side roads trying to localize the squeaks.
We thought the squeaks might be coming from where the windshield meets the RV structure, so we sprayed some silicone into the rubber seals that hold the windshield in place along the bottom of the windshield.
We then went back inside and took the dash apart, starting with the strip of screws running along the top of the dash, and found that all the screws were hitting home into solid structure, so that wasn't the problem. We starting taking the dash apart and we hit a wood "firewall" (for lack of a better term) that we would have had to cut through in order to get to the spot where the dash was squeaking. We didn't want to make a cut through that (yet), so we found the other side of the wood firewall through the front hood. The area that we thought might be squeaking was way up in the corners, covered with a huge sphere of expanding foam in a very difficult to reach area, so we went back inside.
My buddy took his drill and drilled a hole in each corner of the dash, right where the arrow is pointing in the attached picture. He drilled in the same spot on each corner of the dash. The picture I included is just the point where he drilled on the right hand side. We drilled in the same exact spot on the left hand side.
We thought about filling that entire area with expanding foam to kill the squeak, but we were afraid that if we did that and it didn't solve the problem, now our squeak would be permanently encased in expanding foam and we'd never be able to fix it.
So we started driving again. He took a can of silicone lubricant with the straw applicator and started spraying into those two drill holes, trying to aim where the squeak was coming from. I think we dumped about 1/4 of a can into each hole, just spraying around in that area. After probably 5 or 10 minutes of driving, the squeak slowly went away, so I'm assuming the silicone liquid worked its way into whatever crack was causing the squeak over time as we were driving. I'd say the squeaks are about 90% gone now. We then placed a black grommet into the holes for cosmetics.
I haven't driven the RV since, but have a trip planned this weekend. We'll see if the squeaks come back. If I have to dump some silicone into the holes once a while, so be it. Those dash squeaks were the last squeaks left in my RV so now I'm going to have a silent runner : )
2013 Fleetwood Excursion 33A
Cummins ISB 6.7L (ISB 10)/Allison 2100 Transmission
Freightliner XCS chassis