I recently purchased a retired 2017 police silverado with a bad transmission. Currently at the shop and they just called me to let me know the initial estimate might not be acurate as the unit could not be rebuild and is was a 6l90 and not the more common 6l80. The label on the side of the has the following code. 5CKA which according to the info on the forum the C means its an 80 not a 90. How else can I verify whats the correct transmission. According to the title it is a 2500 series but it has a 5.3 and only six lugs so this option of "2500" might be only offered offered here in Mexico where I am located. So it is possible a transmission is too damaged to be rebuild and how do I identify it.