Y = 4001~5000 GVWR weight class, hydraulic brakes, driver and passenger air bags.
Look at the upper right of the door sticker for the exact GVWR of this particular truck.
Originally Posted by peashooter
The truck is a 2001 standard cab step side 4.0 4x4 auto.
I is not an XL because 4.0 was not an available option.
Some 2001 model clues to look for:
MOST 4x4 XLT had textured gray fender flare trim
Exceptions: XLT 4x4 Value Package had no added fender flare trim, front or rear, Flareside box trucks had no added fender flare trim, front or rear.
MOST 4x4 Edge had smooth color-matched fender flare trim.
Exception: Edge w/ Flareside box had no added fender flare trim, front or rear.
4x4 XLT = carpeted or textured vinyl floor
4x4 Edge = hexagon pattern vinyl floor
4x4 XLT = chrome bumpers
4x4 Edge = color matched painted bumpers
Obviously, any of the above could have been swapped out in the interim. There still might be enough evidence to make an ID.