ploughboy

I ordered the "Spring Thing " for $45 but haven't installed them yet. In the meantime, I'm living with the noise which only happens at slow speed when just getting going, not when underway at speed. Still amazed that undercoating would result in this problem which the dealer didn't offer to fix as it was my fault for undercoating the truck! Will report on the "Spring Thing" fix after I get her up on the lift. Too busy getting ready for winter here and thinking about another dealership!

Hi All, Thanks for your replies. When I asked what the fix for the knowing was, the dealer here quoted me $1,600 to replace the rear springs. When it was clear I wasn't going there, they said they would recommend power washing the springs and greasing them like crazy so they don't flap. Looks like that idea would be worse than undercoating oil which doesn't seem to attract road gravel. Initially, they said my undercoating degraded the rubber spacers on the springs. However, the rubber spacers are still there and look to be in perfect shape. They did check the rear end which is where I thought the problem was and said no, it was simply the springs. After looking around on the net, I found "Spring Things", basically a heavy piece of rubber with a heavy duty zip tie to hold the rubber between the springs for $45. I will give that a try after power washing the springs first and let you know how it goes. What amazes me about this is that the problem has been ongoing for GM for years and they haven't done anything about it! Instead, they say there is a bulletin to dealers saying don't allow undercoating on the springs. Better to let them just rust? Very strange! The truck is still very comfortable, but makes a lot of noise at low speed now. You would think that a truck they ask what $80,000 or more for now would be better built? I also have a 2002 extend cab 2500 which I get undercoated annually and never have had any problems with the springs. Thanks!

Hi All, I have a 2020 GMC AT4 Diesel and it just recently started having a clunking sound, most noticeable at low speeds over uneven terrain. I took it to the dealer and they asked if I had them do an undercoating. I told them I had it done locally about a month ago. They were clearly wondering if they had to fix the problem or if it was my fault! They then said that the vehicle's spring and frame should not be undercoated as the coating causes the spring spacers to be ineffective (at first they said the undercoating caused the spacers to deteriorate) causing the springs to slap, making the noise I hear. From what I gather this has been a problem with GMC springs for years. Do they ever plan a fix? I was told to power wash the springs, dry and then grease them like crazy. It seems so odd that such a basic problem wouldn't have forced GM to do a fix/recall? Any advice would be appreciated. I love the truck but the noise may force me to get rid of it! Thanks!