Check out this thread. Lists all the differences http://www.dieselplace.com/forum/showthread.php?t=67521 As for telling which you have there is a way to tell by the VIN, one is a letter the other is a number in a certain place. For the life of me I can't remember. SO open the glove box and look at the RPO codes. If there is a LBZ it's an LBZ and of course a LLY will mean you have a LLY. EDIT> Just found it. look at the 8th digit in the VIN, 2=LLY D=LBZ. Also on the rad support of my truck there is a sticker stating the engine. Maybe you can find one as well. waytogo
also the name plate on the door, the lbz says allison trans-duramax. the lly just says duramax diesel. and the lbz is alot faster and tows alot better.
