I ordered my truck in February of 2005. It was delivered to me in April 2005. I have a 2500HD, short bed, extended cab with the allison trans. My questions pertains as to which generation of LLY that it came with. The brochure for the truck and my itemized truck order both list the motor as having 310 horses and 605 lbs tq. On the face of this I would assume that I have the 2nd generation LLY. The only thing is that I have a 5 speed trans. Is there any other way to tell which generation LLY the motor is since both have 9 in the VIN? As a side note, the overheating deal has come to my attention for the first time since reading these posts. Are the overheating engines first generation, 2nd generation or a combo of both. I have had no problems with mine and I tow a 11,000 lb 5th wheel over some pretty up and down roads. Thanks for reponse.

The eighth digit of the VIN is what counts. If a '2' you have a LLY. If a 'D' you have the new LBZ.

If you have the 5-speed Allison transmission, your truck is a 2005 Model Year LLY. The 8th character on your VIN should be a 2.

Early 2006 Model Year trucks were built with the 3rd generation LLY's and the 6-speed Allison transmission and had a 2 in the VIN. Current trucks built with the 6-speed manual transmission also have the 3rd Gen LLY. These also have a 2 in the VIN.

The LBZ's were not produced until AFTER September 15, 2005 and only for 2006 Model Year trucks with the 6-speed Allison transmission. The LBZ's have a D for the 3rd character in the VIN.

ENGINE VIN Code
LB7........1
LLY........2
LBZ........D

as far as generation of LLY the 2nd generation LLY was in the 06s with the 6 speed allison tranny. does this answer your question?


1st generation duramax - LB7 (8th Digit 1) yrs 01-04
2nd generation duramax - LLY (8th Digit 2) yrs 04.5-06
3rd generation duramax - LBZ (8th digit D) yrs 06.5 - current

I hope this helps. The 06 LLY comes with the 6 speed allison tranny, new air intake, new cooling system and a few extra items which are available on the LBZ.