Ok well im starting the hunt for a low mileage junk yard 4l80e, i found one that says they have one out of a 2006 silverado with 26k miles. How can i tell from the exterior what year the 4l80e is?

 

look for a bolt hole at the 12 o-clock position.

 

moved to GM section for you. I do not think you would have gotten an answer in the Ferd section.

 

oops... thanks probably wouldnt have

 

I think as long as you get one that's 2002+ you will be fine (it'll have all the upgrades in it). They have an aluminium tag on them showing the date.

The trans ID plate is on the pass side toward the rear. At the bottom of the tag on the left 1st 2 digits is the year. Next digit is the calendar year. Next 3 digits is the Julian date.
Top left 2 digits is the model
Top right on tag should be the letter P for 4L80E--4L80EHD ( heavy duty )