High ED RPM @75mph in 34F?

[slowjam]

Testdrove a nice Laramie w 3.92 gears yesterday and noticed rather high RPMs on the highway. The truck was warmed up before we left the lot. Took some backroads on a 10 mile ride before hitting the highway. It was a flat stretch and I was looking at the MPG gauge (showed instant 18-19mpg) @75 Mph. Tried to back off on the ”gas” pedal but the RPMs did not go down. I think they should have been in the 1300 rpm range...anyone experienced this issue. It was 34F outside so I’m not sure if the engine was stuck in some kind of hyper-idle mode....was hoping to see the 30+mpg on the dash

 

[SpeedyV]

I’m a little surprised you can get the diesel with 3.92 gears. It makes sense on my Hemi, as it’s happy to sing at 2K+ RPM all day long. But a diesel - even a small one - hmm.

 

[slowjam]

Almost all 2020 ED are spaced out with the 3.92 gears. You have to look real hard to find one with the 3.21

 

[NewLove]

How’s the power of the engine at high speeds?..


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[Wheeler]

Probably went into Regen mode.
That last in between 8 to 10 minute. And truck goes back to normal. You gonna hate those 10 minutes every 300 to 500 miles.

 

[Wheeler]

Forget to mention if u pull up you would be able to smell kind of electric burn

 

[slowjam]

The truck had 30 miles on so I'm not sure if it was going thru the regen or not. I didn't feel good power when I expected to, and a I had a number of diesels over the years so I know when to expect the torque to kick in.
As a side note:
There was a substantial level of diesel noise from the engine bay and nothing from the tailpipe. Kind of reverse from my HEMI. Was expecting some "diesel" sound from the exhaust.

 

[go-ram]

Almost all 2020 ED are spaced out with the 3.92 gears. You have to look real hard to find one with the 3.21

.
Just ordered a 2020 5th-gen Laramie with 3rd-gen Ecodiesel with 3.55 rear diff.
.

 

[SpeedyV]

Almost all 2020 ED are spaced out with the 3.92 gears. You have to look real hard to find one with the 3.21

I thought I read that you could do 3.55s with the ED as well. Is that incorrect?

Edit: @go-ram just answered that question!

 

[Zeronet]

Wouldn’t the RPMs On the diesel be the same as the Hemi on the highway? Same transmission gearing, right? So for 3.92 gears at 75 MPH I would expect over 2000 RPM. The OP was expecting 1300 but I don’t see how that’s possible. Even with a 3.21 I would expect about 1750. He didn’t mention the actual RPM observed at 75.

 

[slowjam]

The RPMs were over 2100 and the mpg was 19. Way south of the 26-29 range I expected to see (and the truck was empty)

 

[Zeronet]

Those RPMs sound about right for a 3.92. I’m thinking you would need to get the 3.21 gears to get the window sticker highway MPG and even then probably not at 75.

 

[VernDiesel]

My 3.92 would turn about 2,100 at 75 and would normally average about 24 on a long highway trip unloaded.

 

[bgmshrm]

My 3.92 would turn about 2,100 at 75 and would normally average about 24 on a long highway trip unloaded.

wonder what they would be with a 295 65 20 . could figure it out but dont want to do the math . No thinking on Christmas.

 

[slowjam]

Took a different ED for a spin and w the 3.92 gears it runs the same RPMs as the HEMI. I guess advertised fuel economy on the window sticker is for the 2x4 and 3.21 rear end....no way to reach 29mpg highway with the 3.92 axel (@70-75mph)
In the end, my expectations regarding the RPM level were not In line with the engine/transmission setup However it is good to know the first truck I drove run as it should have.

 

[NewLove]

Took a different ED for a spin and w the 3.92 gears it runs the same RPMs as the HEMI. I guess advertised fuel economy on the window sticker is for the 2x4 and 3.21 rear end....no way to reach 29mpg highway with the 3.92 axel (@70-75mph)
In the end, my expectations regarding the RPM level were not In line with the engine/transmission setup However it is good to know the first truck I drove run as it should have.

What were you getting?..


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[HST]

Just picked up my ram limited diesel from the dealer and drove it home 75 miles on fast country back roads of floridia and got 28.2 on the lie o meter with 3.92 gear. running between 55 and 70 mph .

 

[OleNavyMane]

Likewise, I bought mine on 12/20. Drove it 115 miles home from dealer at 65 mph mostly. 10 miles or so of the trip was city traffic; I averaged 28.7 per the trucputer.