[muff34]

it is probably the steering gear shaft. this shaft is at bottom end of steering column ,about a foot long slip shaft with a u joint and coupler at each end. had mine done at a garage by a former Gm mech. about an hour`s labour part was $100.00 Canadian. Ask at local Gm garage they should know about it. Also I was told that they used to have a kit for it,to re lube the joints it was a waste of money,just change the whole shaft. I did and the clunck is now gone,and I DID NOT do any cv joints. The car was up on a hoist to do the job, alot easier to work on
hope this helps Good Luck MUFF