I believe that the 2638 pound rating from the pins does not include the bucket, or the quick attach plates, which look to weigh around 138 pounds. I believe this is why we often see 2500 pounds as the max list ratings for this tractor, from the pins.
like I clearly demonstrated with my tractor, I could lift a pallet of 50 bags of 40 pound salt up to a working height.. that also includes the weight of the pallet and my forks, which probably weigh around 300 to 400 pounds and are 42", effectively moving that weight further away from the tractor and make it heavier.
But I also found that lifting from the ground had much more power than lifting from the working height. So, I don't know that I would be able to lift that same pallet off of a trailer or truck bed.