Is this an aluminum shaft? I have wanted to replace the joints on mine for a while, because Im getting a pinging or clicking noise and Im afraid of heating it up too much and melting the aluminum. After searching for a while I came across this website
http://www.f-body.org/faq/4/4_3.htm Click on "I have a 98 or 99 ls1 body....." Im now thinking this is what Im hearing.
Just thought Id throw it out there as another possibility.