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6.7 Cummins vs 6.6 Duramax

SoonerWing03
Explorer
Explorer
As someone who knows next to nothing about Diesel engines, I am trying to figure out the strengths and weaknesses of these to. Any opinions would be appreciated.
87 REPLIES 87

ng2951
Explorer
Explorer
Having an 07 Dmax, I like it. There are some quirky things about it, but I don't know if it has had more problems than my friends' Dodges.

What is bad is that the water pump tends to fail punctually at 160K miles, but it fails slowly giving you lots of warning (leaking) giving you time to get it into the shop.

The other weird problem on the 3/4 ton is running it at high altitude, load, and heat. There can be an occassional problem where the engine will flip into limp mode because the fuel hose can get soft and start to collaspe starving the engine for fuel. Let it cool for a couple of hours and the problem will self fix and the shop won't be able to locate the problem!

Another problem on the 3/4 ton is the primer on the fuel filter. Every few years the rings start to leak and you will need to replace them. The new assy cost about $900, the rings cost $13 and take an hour to replace. Fairly easy to do.

The solenoids on the 4 wheel drive system can get weak. Those are about $250 in parts, and if you have a lift can be replaced in about 1 or 2.

Beyond that it runs pretty darn good, and better than my friend's younger Powerstroke. (leaky injector bent a piston rod).

My mechanic tells me that today he could get me what I paid for it used years ago because some people want that LBZ engine. My mechanic also says I have another 250K-300K miles left in it.

What I will say is that there is nothing like 4WD and a turbocharged diesel for towing, even though I could probably pull the current RV with a gasser.
Foard County News & Sassy Schoolmarm
with Chloe, Belle, & Danke
2017 GD Imagine 2800BH
2017 53 days camping
'07 GMC Sierra 2500HD Classic 4x4 LBZ Duramax Diesel
Honda 2000sThe Bayou Bounty Hunters Cowboy Club
The Single Action Shooting Society

FishOnOne
Nomad
Nomad
ShinerBock wrote:
Is it the same people that told you that the 2019 Cummins was not going to have an EGR? If so then I would stop listening to them.


I recall it was a special cummins lady giving a tour. The way I understand this went down is she was winking at him and blowing kisses in his ear while whispering that the CP4.2 was coming, but somehow that got translated to downstream EGR, crazy HP and torque increase and the "new green deal" fuel economy performance recognition award.

Crazy stuff...
'12 Ford Super Duty FX4 ELD CC 6.7 PSD 400HP 800ft/lbs "270k Miles"
'16 Sprinter 319MKS "Wide Body"

ShinerBock
Explorer
Explorer
Is it the same people that told you that the 2019 Cummins was not going to have an EGR? If so then I would stop listening to them.

If something like a valve body is broke and did not cause clutch or any other damage, then we replace the valve body, not the whole transmission. The only time the whole transmission is replaced if is beyond repair or the cost to repair is more than a new one. In that case the bad one gets sent back to Aisin (IF that is where we purchased the new transmission) as a core so they can re-use the case and other parts. In many cases they just want the core back so other re-builders don't get their hands on them like Revmax and Suncoast who both have built versions of the Aisin.
2014 Ram 2500 6.7L CTD
2016 BMW 2.0L diesel (work and back car)
2023 Jeep Wrangler Rubicon 3.0L Ecodiesel

Highland Ridge Silverstar 378RBS

Cummins12V98
Explorer III
Explorer III
Going by reports and from a parts manager I know.
2015 RAM LongHorn 3500 Dually CrewCab 4X4 CUMMINS/AISIN RearAir 385HP/865TQ 4:10's
37,800# GCVWR "Towing Beast"

"HeavyWeight" B&W RVK3600

2016 MobileSuites 39TKSB3 highly "Elited" In the stable

2007.5 Mobile Suites 36 SB3 29,000# Combined SOLD

ShinerBock
Explorer
Explorer
Cummins12V98 wrote:
ShinerBock wrote:
Speaking of Aisin, we just had two in our mobile service truck 5500s replaced at one of our Ohio dealerships. Failed line pressure solenoid from what my corporate fleet manager said.


Very few issues with the AISIN. If there is an issue they simply replace and send to Factory.


I am not sure where you are getting this info from, but that is not what we do at our 120 dealerships. There are also more than "very few" issues in the medium duty trucks that we sell/service with Aisin transmissions. I hate to burst your bubble because I know how adamant your are about whatever you own being the best in the world.
2014 Ram 2500 6.7L CTD
2016 BMW 2.0L diesel (work and back car)
2023 Jeep Wrangler Rubicon 3.0L Ecodiesel

Highland Ridge Silverstar 378RBS

FishOnOne
Nomad
Nomad
Cummins12V98 wrote:
FishOnOne wrote:
Cummins12V98 wrote:
Ok Skid

What about the true Medium Duty AISIN?


You mean the one used in the Nissan Titan...


No silly!


LOL... Someone had to ask the question. :B
'12 Ford Super Duty FX4 ELD CC 6.7 PSD 400HP 800ft/lbs "270k Miles"
'16 Sprinter 319MKS "Wide Body"

skidooman93
Explorer
Explorer
ShinerBock wrote:
If I am not mistaken, the 6.4L used a Siemens K16 VDO HPFP, not a CP4.


My bad, yes the 6.4 ford used the K16 pump. Which was half the reason the disaster the 6.4 turned out to be. The other half were the injectors

The late model 16-present cp4 pumps have been much better I haven't done an inspection on a 6.7 ford with a failed pump in a awhile.

As far as trannies go. In 12 years of inspecting I've looked at 1 Alison. Then a couple dozen torque shifts (until recently) and 68 RFE's. What saves the Alison is they shut themselves down and go into limp in really easy before stuff gets torn up. VS the Torque Shift that goes and goes until it grenades. The 68's are some where in between. I have never looked at an Aisan but they aren't that terribly common so I cant comment much on them. The most recent 6 speed torque shifts seem to have a problem with the rear planetary. I have seen half a dozen school buses and as super duties that have torn up trans because of a rear planetary failure.

In my opinion I wouldn't worry about the transmission in any of the GM, Ford, or Ram 2500-3500 trucks as long as the engine is kept at its stock power levels.
2015 Ram 2500 SB 6.7 Cummins, 68RFE Rear Air Suspension
2015 Ram 2500 SB 6.4 Hemi 4.10's Rear Coil Springs (Sold)
Anderson UCH
2014 Open Range 367BHS
1 wife, 1 Son, 1 Daughter, 1 Red Lab that wont come in the camper because hes a big baby, so he stays home.

Cummins12V98
Explorer III
Explorer III
FishOnOne wrote:
Cummins12V98 wrote:
Ok Skid

What about the true Medium Duty AISIN?


You mean the one used in the Nissan Titan...


No silly!
2015 RAM LongHorn 3500 Dually CrewCab 4X4 CUMMINS/AISIN RearAir 385HP/865TQ 4:10's
37,800# GCVWR "Towing Beast"

"HeavyWeight" B&W RVK3600

2016 MobileSuites 39TKSB3 highly "Elited" In the stable

2007.5 Mobile Suites 36 SB3 29,000# Combined SOLD

Cummins12V98
Explorer III
Explorer III
ShinerBock wrote:
Speaking of Aisin, we just had two in our mobile service truck 5500s replaced at one of our Ohio dealerships. Failed line pressure solenoid from what my corporate fleet manager said.


Very few issues with the AISIN. If there is an issue they simply replace and send to Factory.
2015 RAM LongHorn 3500 Dually CrewCab 4X4 CUMMINS/AISIN RearAir 385HP/865TQ 4:10's
37,800# GCVWR "Towing Beast"

"HeavyWeight" B&W RVK3600

2016 MobileSuites 39TKSB3 highly "Elited" In the stable

2007.5 Mobile Suites 36 SB3 29,000# Combined SOLD

blofgren
Explorer
Explorer
ShinerBock wrote:
Speaking of Aisin, we just had two replaced in our mobile service truck 5500s replaced at one of our Ohio dealerships. Failed line pressure solenoid from what my corporate fleet manager said.


Yikes. Any idea of the cost?
2013 Ram 3500 Megacab DRW Laramie 4x4, 6.7L Cummins, G56, 3.73, Maximum Steel, black lthr, B&W RVK3670 hitch, Retrax, Linex, and a bunch of options incl. cargo camera
2008 Corsair Excella Platinum 34.5 CKTS fifth wheel with winter package & disc brakes

Bionic_Man
Explorer
Explorer
FishOnOne wrote:
Cummins12V98 wrote:
Ok Skid

What about the true Medium Duty AISIN?


You mean the one used in the Nissan Titan...


I think the comments about "medium duty" engine and tranny really aren't valid arguments, especially when the person who makes them can't seem to explain why that makes them better. I also know that the Aisin A466ND used in the Nissan isn't the same as the AS69RC that is in the RAM.
:S
2012 RAM 3500 Laramie Longhorn DRW CC 4x4 Max Tow, Cummins HO, 60 gallon RDS aux fuel tank, Reese 18k Elite hitch
2003 Dodge Ram 3500 QC SB 4x4 Cummins HO NV5600 with Smarty JR, Jacobs EB (sold)
2002 Gulf Stream Sea Hawk 29FRB with Honda EV6010

FishOnOne
Nomad
Nomad
Cummins12V98 wrote:
Ok Skid

What about the true Medium Duty AISIN?


You mean the one used in the Nissan Titan...
'12 Ford Super Duty FX4 ELD CC 6.7 PSD 400HP 800ft/lbs "270k Miles"
'16 Sprinter 319MKS "Wide Body"

ShinerBock
Explorer
Explorer
Speaking of Aisin, we just had two in our mobile service truck 5500s replaced at one of our Ohio dealerships. Failed line pressure solenoid from what my corporate fleet manager said.
2014 Ram 2500 6.7L CTD
2016 BMW 2.0L diesel (work and back car)
2023 Jeep Wrangler Rubicon 3.0L Ecodiesel

Highland Ridge Silverstar 378RBS

Cummins12V98
Explorer III
Explorer III
Ok Skid

What about the true Medium Duty AISIN?
2015 RAM LongHorn 3500 Dually CrewCab 4X4 CUMMINS/AISIN RearAir 385HP/865TQ 4:10's
37,800# GCVWR "Towing Beast"

"HeavyWeight" B&W RVK3600

2016 MobileSuites 39TKSB3 highly "Elited" In the stable

2007.5 Mobile Suites 36 SB3 29,000# Combined SOLD