I just had the Sun Shell (GM 4L60E) in my transmission replaced on my 2002 Envoy with 63,639 miles on the vehicle. The repair shop gave me the faulty part and a letter explaining that the transmission in my vehicle failed because the sun shell spines were stripped. Apparently, this is not uncommon in the automatic transmission repair business. The repair shop explained that this part is known to contain a softer alloy, which is highly prone to stripping. I did not purchase an extended warranty, but feel that GM should be accountable for using parts that are known to fail. Has anyone else encountered this problem? Could you please let me know what you did to resolve and the outcome of your efforts? Thank you.