While the Duramax may not be the loudest or the most high preformance diesel engine on the market, Izuzu and GM have done a very good job designing this engine. The Best part of these engines by far is the transmission. Allison makes trannys from everything to military to these trucks, which use the Allison 1000 and are the best automatic trannys you can buy. I have driven a few Druamax diesels in my life and from what I have experienced I have no complaints. The acceleration was very surprising and shifting was the smoothest I have ever felt in my life. If you ask me these are very reliable engines that will always get the job done for you. Over the years Duramax has produced about 5 series of the engine the earlier LB7 and LLY, then came the LBZ and LMM and the most recent LML. All of these blocks are 6.6L and never had any major problems in production like the 6.0L powerstroke did. Even though I am a true Ford guy if I had to buy one of these trucks I wouldnt think twice between the Allison trannys and GM's new LML that puts out 397hp and 765 ft lbs of torque!........yea you heard me 397hp stock, let me put it this way if you wouldnt buy one of these trucks you can go drive your ricer and I'll roll coal in your window at the next red light.