Heads up on 6.7 Cummins

[Mike D Texas]

Yes. Post 2018, they went to a pickup-specific engine architecture. Details are all over the internet. The 68RFE transmission sucks. Aisin is an excellent transmission. 2016 to 2018 6.7 is the best diesel engine ever put in a pickup truck - now let me go find some cover to duck all the flak I'm about to get.



Jury is still out. Engine was re-designed again for 2025. They have the 8 speed transmission which is a vast improvement over both the RFE and Aisin. Probably the best transmission on the market right now. The engine shares a lot of the features that made the 2019 to 2024 engines suck, with the addition of a modified CP4 fuel system. Why makers just absolutely insist on using that stuff I can't understand. It's supposedly upgraded and has a different name, but it sure looks a lot like a CP4 to me. The 25's have glow plugs instead of a grid heater so this bolt thing goes away. Broken off glow plugs are just as bad. We shall see. Me personally, I'd wait a couple more years and see or if you need to buy now, Chevy probably has the most dependable diesel driveline right now. Ford's is also pretty excellent and the power is absolutely stupid.

I guess I need to tell my 2012 68RFE with 267,000 miles on it that it sucks, especially since it’s been behind a deleted and tuned engine for the last 167,000 and towing a 12,000# 5th wheel camper all over the country.

 

[Choupique]

o tell my 2012 68RFE with 267,000 miles on it that it sucks

Good, I'm glad you're happy with yours. Sounds like the grid heater bolt is a non issue, since yours hasn't fallen into the engine yet?

The 68RFE sucks for this application. At the very best, even if it lasts 5 million miles, the engine's performance is severely limited in order to protect the transmission behind it. That's why it flare shifts and why you don't get full engine torque to the ground in any gear except 4th, and even then in only certain conditions.

It's under-built for the engine turning it and the duty cycle the rest of the truck is supposed to be designed for.

 

[prairieboy]

The main problem is you have a post-covid stellantis truck wrapped around the engine, and it's no cheaper than the other two maker's products. The post 2018 engines really aren't THAT bad since they went back to CP3 fuel pumps. They had some lifter problems but I think that was mostly due to people using 15w40 oil. The rest of the truck is really a POS compared to the fords and chevrolets though. When a dodge was cheaper and came with a true industrial engine in it, it was more palatable. At their current price point, no thank you.

How does the oil cause the lifter failure? what oil should they be using?

 

[Choupique]

How does the oil cause the lifter failure?

2019 and later Cummins 6.7 engines in the ram trucks have hydraulic lifters and call for 5w40 or 10w30 (I think) synthetic diesel oil. Traditional 15w40 conventional oil doesn't pump well cold, and it causes all kinds of problems with the lifters on startup and warmup.

If you have a hydraulic lifter diesel, very important to use the correct oil viscosity for the ambient temps you will use it in, and use of a pre-heater helps a lot as well. Warm oil is happy oil.

And as always, RTFM.

 

[Turkeygetpwnd38]

Ram still does not have a fix for the HCU recall. Dealers can't sell the trucks with an outstanding recall. Weird that they come up with a fix after 2-3 years. Just had mine in for Homelink and they said no parts available for the recall. They are still trying to get you to do the emission's upgrade, No way for me, my 18 runs just fine the way it is.

Yup I've replaced mine twice on my dime. The only other option was drive it and let it ding error messages 10 times a minute. The latest one I replaced will likely go out eventually because it wasn't a new "fixed" unit since they still weren't available.

 

[Mike D Texas]

Good, I'm glad you're happy with yours. Sounds like the grid heater bolt is a non issue, since yours hasn't fallen into the engine yet?

The 68RFE sucks for this application. At the very best, even if it lasts 5 million miles, the engine's performance is severely limited in order to protect the transmission behind it. That's why it flare shifts and why you don't get full engine torque to the ground in any gear except 4th, and even then in only certain conditions.

It's under-built for the engine turning it and the duty cycle the rest of the truck is supposed to be designed for.

I can concede to the shift flare issue but the performance even towing has not been a detriment for me at all. I haven’t noticed the need for full power shifts.

From what I’ve seen, most of the people destroying their 68RFE is because of them running wild tunes, powerbraking, boosted 4WD launches, etc. I know of several hotshot drivers that have gotten hundreds of thousands of miles with their 68RFE pulling heavy loads.

I think the key takeaway is don’t act like an idiot and it will service most people just fine.

Is it the ideal transmission, no it’s not. But it doesn’t suck in my experience.

 

[Mike D Texas]

2019 and later Cummins 6.7 engines in the ram trucks have hydraulic lifters and call for 5w40 or 10w30 (I think) synthetic diesel oil. Traditional 15w40 conventional oil doesn't pump well cold, and it causes all kinds of problems with the lifters on startup and warmup.

If you have a hydraulic lifter diesel, very important to use the correct oil viscosity for the ambient temps you will use it in, and use of a pre-heater helps a lot as well. Warm oil is happy oil.

And as always, RTFM.

As I recall the 19-21 model trucks had a double or maybe even a triple whammy;

CGI engine block
CP4 fuel pump
Hydraulic lifters.

Seems like they went back to the CP3 for 22-24 models and back to iron block in 2025? Are they still using the hydraulic lifters?

 

[Choupique]

the key takeaway is don’t act like an idiot and it will service most people just fine

I agree. I own one. You don't need full power shifts, no automatic transmission can endure that for very long without being rediculously overbuilt. The main problem with it is that it's underbuilt, and the programming to offset that is retarded in the name of driver comfort. It does all that goofy stuff to maintain shift speed and driver comfort. If it would cut fuel, shift, then reapply fuel it could allow higher torque through the driveline, but that would make engine noise every shift and feel like a shift happened. With todays driver comfort standards, we absolutely can't have that kind of stuff.

As I recall the 19-21 model trucks had a double or maybe even a triple whammy;

CGI engine block
CP4 fuel pump
Hydraulic lifters.

Yes, the 19-21 were especially horrible prior to the fuel pump recalls. They went back to CP3 pumps for all of those. The CGI block wasn't really a problem as far as I'm aware. The lifters were problematic at first across the board and now should only be an issue if abused (wrong oil, cold start full throttle, stuff like that).

Seems like they went back to the CP3 for 22-24 models and back to iron block in 2025? Are they still using the hydraulic lifters?

19-24 should all have CP3's now. For anybody reading if you have a 19-21 Cummins and haven't had the fuel pump recall done yet, do it.

The '25 engine has a cast iron block again, I'm not sure if the architecture matches the old one or not. Still hydraulic lifters, a revamped CP4 pump, and glow plugs. Probably quite a few other minor changes I'm not aware of. I believe the ECM is probably 2027 cybersecurity compliant which means it's probably extremely difficult to delete. The CP4 is likely the same revision that Ford is using now, which is dramatically better than old ones. It still aint a CP3 in terms of reliability though. The reality is these things aren't built for durability or reliability at the forefront anymore. They're built to be cheap, quiet, and not shakey. An industrial Cummins engine is none of those things. Solid lifters and CP3 pumps are just too noisy to be acceptable when Ford and Chevy are both making more power and less noise.

Stelantis screwed up big time when they decided they would try to compete with Ford and Chevy rather than stick to what they were good at - being cheaper.