Hey there guys, Yep, not cool at all... been in and out of the dealership 5 times to remedy a loud clunk in rear of 2014 Silverado 2500HD. They thought it was rear axle bearing and inspected, found it was not the issue. After re- torque 'ing' bolts in rear of truck, still clunking when chassis racks side to side as when transitioning over an uneven driveway entrance or other. After I pressured the service department, they said GM recommend replacing the rear leafs... mind you this is with less than 7K on the vehicle which was purchased new... Leafs replaced, still the clunk. In neutral truck running or not, just the motion of the vehicle, it's there. I bring it back, now they claimed a rear shock was defective.. o...k? (Which they would only replace 1, how often does anyone replace one shock?) Still the clunk persists. At this point the service department says they can't figure out the issue!? And mind you this dance has gone on for months and months, for over 10k miles. I AGAIN tried to have the clunking resolved and that's when the excuses started. They started telling me again the leafs?? I said it was done only months ago here!! Apparently their computer system had been upgraded and wasn't showing this prior work... Then surprise surprise , the service manager asks when the FF application had been done, and said Chevrolet does not approve of that undercoating process. He informed me they can only speculate, but were thinking the leaf shackle bushing had been affected by the fluid film and caused it to wear premature?? I thought FF was supposed to be solvent free and not damage rubber or plastics, though after looking at the FF label, it does in fact warn of it contacting rubber surfaces. I feel this is being used as an excuse to deny any further warranty service and am extremely frustrated. The goal was to reduce problems with the vehicle, not create them.! Just something to consider, though if it was not the FF, I believe they would have found any number of other technicalities to weasel out of the proper repair. I have been in communication with corporate GM over this, though I suspect they will also deny further repair after push comes to shove. I have used FF on 3 other older vehicles for a longer period of time without any issues. It does inhibit rust damage... but leaves one vulnerable to denial of warranty service. Anyone else have a nightmare experience like this??