Trans problem solved
 

I own a 2002 GMC Sierra 2500HD Duramax Diesel
and 3 months ago the check engine light came on and would not
shift out of 3rd gear(auto trans).
I took it to a repair shop and after the trans was removed and the trans opened found out this trans is to have 7 clutch dics and mine had 6.
Now after spending $$$$ it is back together and on the road again.
Just wanted to know if any one else has had this problem?
I think Gm needs to pay for this repair!!!! But that won't happen.
Thanks
Sierra 2002HD

I have never heard of this problem... Am I to assume that it is the Allison 6spd with OD?

Yes Allison Trans
2500HD