Are the RPMs about right

[JohnWedell]

We are on our way to Florida. The truck is at the GCWR of 23,000 lbs but runs great (all the numbers are good). I have a question about the rpms. At 65 mph the tac says 2500 rpms. Up a slight incline it goes to 3200 rpms and up a steep grade it goes to 4500 rpms. Does that sound normal. Would the computer let the motor over rev and do damage to it.

[redsnapper]

Sounds about right...….

At 65mph on flat ground and starting a climb, the computer will tell the trans when to shift down.
A downshift will jack up the RPM's and keep downshifting as the climb becomes steeper and the RPM's begin to drop to computer set parameters.

I often used to manual downshift and find a speed/RPM combo that I felt comfortable with, without lugging down, and kept it there until the grade eased off and or over the crest.

I don't know if the computer has the ability to back off dangerously high RPM's.
Your right hand (shifter) and right foot (pedal) is the best control for keeping RPM's in a range that is not screaming tight, and keeps the truck from lugging down.

[TCNashville]

A gas engine pulling that much weight is bound to rev in certain circumstances. I wouldn't worry too much about it as long as you're within the weight parameters of the tow vehicle. I have a 6.2l gas engine in my F-250 and it loves to rev while towing. It was built for that. Unfortunately it'll pass everything but a gas station.

[jimp]

Doubt you are near the redline on the tach, so the ECU is trying to keep the motor in the power zone. It's a bit unnerving to hear the motor rev that high, but should not cause any harm to motor.

[DNelson]

I have the 6.4 but with 373 gears and kind of miss the 390's in our 2009 1500. My guess is your RPMs are fine because mine runs about 2000-2100. From what I have read the design of the 6.4 and transmission is such that you can' t destroy the 6.4 even if you try.

PS: I still wouldn't try.

[Camper_bob]

Gas motors generate the most HP and Torque higher in the RPM band. Take a look at the numbers and you'll see things like "305 HP at 5400 RPM". So, yeah gas engines are meant to rev. That's one reason why a lot of people like diesels. They generate LOTS of torque LOW in the RPM band.

My 6.4 would get up into those ranges every now and again too. I didn't like it too much, but if that's what it took to get up the hill, that's what it took. I was operating the truck well within its design parameters and never had issues.

I would often lock the trans into a lower gear to keep it from shifting if I was traveling in rolling hills, and I found I was able to get better fuel economy even though the engine was spinning faster. Same with my GMC Sierra with the 5.3. The problem with my Ram 6.4 was the 3.73 rear end. It would have been better if I had a 4.10.

And yeah, I could pass everything but a gas station too...

[SkyBound]

The higher RPMs are normal for a naturally aspirated gasoline engine under load. Just sit back and relax and enjoy that sweet, sweet sound of a revving big block V8! I have driven the 6.4L Hemi in a 3500 platform, and I must say there isn't a whole lot there below 3000rpms, after which it really gets going. The higher RPMs circulate fluids faster as well which helps with cooling, which is a good thing going up those hills.