I've got 163k miles on my truck (see signature for intel) and I've started having some minor issues over the past 2 months that have gradually gotten worse and worse. Here are the symptoms...
1) Whenever I'm on the road and take my foot off of the gas pedal, and then re-apply force on the gas pedal---I hear a dull "thump" coming from below the truck. Not only do I hear a "thump" but you can also feel a slight vibration too. This only happens when i re-apply gas after letting off of it.
2) I've now noticed that this "thump" also occurs when I'm parked, and then move the transmission into Drive. Once the transmission changes gears, I hear and feel the "thump" again.
3) I've been getting some vibrations whenever I'm at 45 mph, very feint but definitely there. The vibrations have also moved to around 50 mph now. And if I'm trying to go over 75 mph, the vibrations get severe.
I was originally thinking that something came loose from the exhaust system, which would explain the "thump" from me getting back on the gas. But now after noticing the "thump" whenever I simply put the truck in Drive, I'm thinking this is a U-Joint dilemma--which would also explain the vibrations at various speeds.
Let me know what you guys think. I'm going over to a friend's house either this week or next to take a closer look. I've used the search function here, but can't seem to find similar symptoms to what I'm having. Thanks guys!