6.4 hemi not shifting into 8

[AH64ID]

It’s not an issue with 4.10 gears.

I noticed the same thing with a rental JL with 3.45’s vs the wife’s JT with 4.10’s. The JL still got insanely good mileage for hardly ever using 8th.

Well, I'm so glad that you have all the world's problems solved. But you don't know your ass from a hole in the ground. If you can't come up with an actual, reasonable answer to a problem, that obviously exists, then you are definitely wasting my time. Obviously you can't, or you would have.

There isn’t a problem, it’s working as designed. Just because you don’t understand that and don’t like it doesn’t make a problem with the truck, it’s a problem with you and your understanding. There isn’t anything else that can be said to you besides it’s working as designed. The design engineers don’t want the truck only turning 1400 rpms at 55mph, it’s really that simple.

Time for you to check your attitude, be polite with the people that are all telling you the same thing, get over it and move on.

 

[J. Reacher]

 

[24hemi]

I bought a 2500 hemi with 3.73 gears and was surprised it reved about 2100 on the highway and fuel mileage wasn’t great. I started wondering if it was in 8th gear and after shifting it to 7 the rpm stayed the same.after playing with the gears I got it to shift into 8 and the mileage was a lot better and rpm’s went down to about 1600. The problem is it didn’t last and went back to only running in 7 on the highway. Any advice?

I just bought a 2024 and am having the same problems. I previously had a 2019 6.4 hemi 8 speed that would shift to 8th at a much lower rpm, and I got much better fuel mileage. I believe the engineers have changed the shift points. The motor will break in and improve MPG around 10,000 miles but it will not be great with new shift points. I do not recommend the 6.4 to anyone living in flat country now that they have changed the tune on the transmission unless you drive above 68 mph all the time.

 

[flan]

Does the same guy keep registering under a different name to post the same story or am I crazy?

 

[michigan dave]

I've driven the 8 speed trans with Hemi for 120k miles in my 2016 and it always utilized 8th gear above 55mph. I got good mileage (20) and it was running perfect when I sold it to buy my 2024 Ram 6.4 with 342 gears. In 1000 miles I've only seen it shift into 8th gear a few times, and my mileage is 15mpg on a good careful day. There is no good reason I can think of to run down the highway at 65mph turning 2000 rpms without a load. You all can make excuses and say its running as designed all day.....The facts are in my opinion, the shift points are not correct for normal every day driving. This is a very informative forum, and many topics will be controversial. Were all just trying to utilize our trucks to the best of their abilities, and not put up with mediocracy.

 

[flan]

Not again

 

[raven_dt]

I purchased a 2024 2500 Tradesman 6.4/3.73 in Oct., mechanically identical to a 2021 2500 Big Horn 6.4/3.73 that I traded in earlier in the year. I also had a 2019 1500 5.7/3.92 that had the 8HP75. The 21 would shift into 8th gear nominally under low throttle/50+mph situations. There is a hill that would always cause an 8 to 7 downshift in the 21. The 24 doesn't downshift on that hill because it's in 7th instead of 8th gear. Ram has changed the programming of these transmissions. The engine will go into eco mode at 50+ mph but not shift into 8th gear??? The 1500 would routinely shift into 8th too. And my mpg is less, ~9%, in the 24 than it was in 21, same driving routine.

 

[raven_dt]

I've driven the 8 speed trans with Hemi for 120k miles in my 2016 and it always utilized 8th gear above 55mph. I got good mileage (20) and it was running perfect when I sold it to buy my 2024 Ram 6.4 with 342 gears. In 1000 miles I've only seen it shift into 8th gear a few times, and my mileage is 15mpg on a good careful day. There is no good reason I can think of to run down the highway at 65mph turning 2000 rpms without a load. You all can make excuses and say its running as designed all day.....The facts are in my opinion, the shift points are not correct for normal every day driving. This is a very informative forum, and many topics will be controversial. Were all just trying to utilize our trucks to the best of their abilities, and not put up with mediocracy.

Based on my experience, Ram has changed the programming of the 8HP75.

 

[whitexc]

Based on my experience, Ram has changed the programming of the 8HP75.

You could very well be right. His 2016 didn’t have the 8spd so it’s not comparable. That said I notice the same thing quite often in my ‘21 in that the truck will go into ECO mode but not be in 8th gear. I hit the gear selector buttons to verify this. I try to eliminate ECO as much as I can remember to. She isn’t exactly a saint on fuel either lol.


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