I have a 2008 Tundra Crewmax 4x4 TRD that is about a month old. I noticed the "clunk" sensation right away. I brought it to the dealer, and was told they were unable to reproduce it and that everything checked out ok. It continued to clunk, and drive me crazy (very annoying). I was close to the dealer and it was doing it, so I stopped and asked to have a Service Tech drive with me. He could feel it right away.
I left it with them the next day (06/20/08) and told them to look at the splines on the driveshaft, as I read on this forum about that being a possible issue. They informed me that Toyota was releasing a service bulletin on Monday, and that they would need it to properly address the issue. I dropped it off for the day and was told they installed a new driveshaft and support bearing and that it was taken care of. I just called them yesterday to say the problem has not been fixed. I will just keep bringing it back until something is done. Love the truck, hate the clunk!
