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?