If you had issues with your 5.9 and did not like it I would not even consider a 6.7. A lot of people are having issues with the emissions junk on them.
I bought a 2008 brand new, and had a ton of issues. The problem is the 6.7 have a DPF, CAT, NOX filter, and a EGR system. The DPF collects soot which then has to be burned off every 100 miles or so it all depends on your driving. This causes extra fuel to be burned in order to clean it out. The MPG on the 6.7 is VERY low in fact I think it can even be less them a hemi in a 2500 since I have owned both that is what I have experience. The other big issues is the head gaskets. I will get into that later.
To resolve some these issues you can delete the emissions equipment which is illegal and will VOID your warranty, but you mpg will go up and so will your reliability. They can cost anywhere from $600 and up. If you add any power to these 6.7 you take the chance of your head gasket going out. When they increased the bore on the 5.9 now there is less surface area between the cylinders for the gasket. Guys are putting in 625 ARP head studs, and even then some still have issues. I have even seen stock head gaskets go out.
Really it would take forever to write a post about all the issues they have as they compare to the 5.9 trucks. One other big issues is the transmissions. They use a G56 for the manuals which has a dual mass flywheel that is VERY weak (2005 and up even the 5.9 have this tranny), and cost about $1,500 to replace that and the clutch to hold even stock or slightly over stock horsepower. The Auto's seem to be better, but then again they have had issues as well it is still a Dodge tranny and you know there history on them. They are going to put the 68RFE in the hemi 2500's in 2012 and call is a 66RFE. It would be really good with the hemi if it is in a 800 lbs of torque cummins. It should hold for a long time.
Other people on other forums will tell you they are great, and you may get one that is pretty good but they don't even compare to a 5.9 when it comes to reliability. It is only a matter of time when you have emissions issues on a 6.7, and they are nothing compared to a gasser truck to fix. All the crap on them cost a ton of money to fix, and just the keep the air a little cleaner.
Here is what went out on mine.
I had to delete all my emissions crap to keep it on the road several trips to the dealer for emissions issues.
Rear Window seal
I pulled 10K lbs all the time as well so this truck was not city driver.
I am sure I am missing a few things, but that was in 36K miles. All the new diesel trucks have these issues, so I would never buy anything other then a 5.9 or even a Ford 7.3 any year even the VP44 years. Replacing a $1,000 VP44 is nothing compared to the cost of the issues of a 6.7. I have owned 5 5.9 cummins trucks, one 6.7, and 1 hemi. I have a friend who is in the same boat as I was with his 6.7 a ton of issues and can't get it sold no one wants them. I have several other friends that still own 5.9's and will not even consider selling them after all the issues we have had with the 6.7 trucks.
Good luck, but is it really worth the extra money anymore to buy a diesel. Unless you are pulling over 10K lbs often a hemi will do the job easy with far less issues and next year you can get a 6 speed with it for far less money then a 6.7.
You can go on cumminsforums.com and check out the issues. Some guys over there really hate me, because I tell it how I see it with the 6.7. If I owned a good product I will tell you how proud I am of it, if I own a POS I will let you know that as well. Just look at the powertrain section on cumminsforums.com and see all the issues people have ever day. Then compare it to the post on this site about the hemi. You will see really quick why I now own a 5.7 2500 hemi truck.
Last edited by evan4434; 07-27-2011 at 10:21 AM.