Griff, I was impressed you had a 2001 with 61k until I looked at the date of the original post :)

Are you in 4x4? I didn't read all the posts so don't attack me if posted already. Well just read the posts.........old shi t

You should check the U-joints.

Griff. Thank you. I love this truck and just aquired it last year at 80000 from a helicopter engineer friend. The famous clunk was in effect but now has subsided and is replaced by the shudder you described so perfectly in your old thread
I was just about to go the slip yoke route. And still may.
I will now include the u joints. Do you recall which and how many? If not all.
I will start my ujoint education now.
Thank you very much again
John

I had all the U joints replaced and the problem was solved.

I wish. I traded that truck in 2010 with about 140k for my current truck.
I have virtually the same truck in 2007 2500HD Classic 8100/allison and it has about 125k on it.
Never had any U joint issues with this one.