What causes my transmission to shudder when I'm towing a 16,000 lb fifth wheel?

Hello, when does the "shudder" occur, and for how long? If you are talking about a shudder on acceleration, especially more aggressive acceleration, it could be due to the driveline angle setting. The angle of the drive shaft can be adjusted depending on need. consider that the suspension compresses in different ways when you accelerate hard. This changes the angle of the drive shaft in relation to the transmission and rear differential. This can cause rotational vibration which you will feel very strongly at times. The problem is -- if you set it too far in a different direction, it can cause vibrations at other times. It's important to measure everything when the load you most always pull is being replicated, and even then, finding a healthy balance between laden and unladen experience is important. If you are speaking of a different kind of shudder, please advise back with further details.