Took the plunge - Cummins to Hemi 6.4

[nirion]

After reading posts, reviews, specs, watching videos, and a few test drives, I finally decided to take the plunge. I sold my 2003 Ram 2500 QC LB 4x4 Standard output 5.9 Cummins 5 speed and bought a new 2014 Ram 2500 Big Horn CC LB 4x4 Hemi 6.4 with 4.10 gears in Western Brown.

It has the 5th wheel prep, so I had to order a new base for my B&W companion hitch. It should be here Friday and I hope to do some test towing this weekend. We leave for our first big RV vacation soon, a trip to Disney's Ft Wilderness on 10/18. I'll post back with more info after the test pulls and hopefully a trip to the scales.

Thanks to all, but especially ib516, for the info on the 6.4. I went back and forth between 3500 SRW Cummins or a Hemi 6.4. I really hope I made the right decision. 🙂

[Buck50HD]

MM49 wrote:
Bigger engines can pull a taller gear set. My 6.4l pulls an 8200lb TT with respect. It works hard at times, but feels very good.
MM49

Or, big engines with tall gears perform worse than small engines with the right gears. But this only applies in certain situations, like fully loaded and steep grades.

[MM49]

Bigger engines can pull a taller gear set. My 6.4l pulls an 8200lb TT with respect. It works hard at times, but feels very good.
MM49

[ib516]

blderman wrote:
Here is a brief example based on trans/rear end gear ratios. I know this isn't proof of anything but it shows the design flaw, in my opinion.

Ram 6.4 (420ft lbs @ 4000 rpm)

1st Gear 3.23= 1,356 ft.lbs x 4.10 rear= 5,559 ft.lbs
2nd Gear 1.84= 772 ft.lbs x 4.10 rear= 3,165 ft.lbs


Chevy 6.0 (380ft.lbs @ 4200rpm)

1st Gear 4.03= 1,531 ft.lbs x 4.10 rear= 6,277 ft.lbs
2nd Gear 2.36= 896 ft.lbs x 4.10 rear= 3,673 ft.lbs


So mathematically speaking the Chevy has 718 ft.lbs more in 1st gear and 508 ft.lbs more in 2nd gear. If my math is correct that is a substantial difference in torque to the rear wheels. If the Ram had the same gear ratios as the Chevy it would have walked away easily.

Your numbers are slightly off - not that it would make much difference. The 6.4L Hemi is rated at 429 tq, not 420.

When you look at the tests results I posted above, if the paper figures translate to real world performance, the GM should have been faster when compared to the RAM in any test that had the trucks compared when in 1st or 2nd gear. My 4.10 equipped truck shifts out of 1st at 40 mph, and will go to about 72 mph in 2nd. So, any test that went to 40 mph or 60 mph, the Gm should have been faster, but it wasn't.

I think it has to do with the engine calibration when at high altitudes. The Davis Dam grade and the 7.2 grade they used at the Milford proving grounds don't show a performance deficit for the RAM, and they involved towing and empty runs going uphill. The only common denominator is the high elevation.

[ib516]

Bigfoot affair wrote:

blderman wrote:
Here is a brief example based on trans/rear end gear ratios. I know this isn't proof of anything but it shows the design flaw, in my opinion.

Ram 6.4 (420ft lbs @ 4000 rpm)

1st Gear 3.23= 1,356 ft.lbs x 4.10 rear= 5,559 ft.lbs
2nd Gear 1.84= 772 ft.lbs x 4.10 rear= 3,165 ft.lbs


Chevy 6.0 (380ft.lbs @ 4200rpm)

1st Gear 4.03= 1,531 ft.lbs x 4.10 rear= 6,277 ft.lbs
2nd Gear 2.36= 896 ft.lbs x 4.10 rear= 3,673 ft.lbs


So mathematically speaking the Chevy has 718 ft.lbs more in 1st gear and 508 ft.lbs more in 2nd gear. If my math is correct that is a substantial difference in torque to the rear wheels. If the Ram had the same gear ratios as the Chevy it would have walked away easily.

LOL! So how do you explain the Chevy going up the Ike in second gear? It only shifted into first just before the top of the mountain.

Face it, the Ram 6.4 is all paper #'s and was beat by a engine trans combo that was put into these trucks back in 07.

How do you explain the other tests results then if the numbers are "all paper"?

Here are the graphic representations of the results for all of the testing done by Pickuptrucks.com - excluding the Eisenhower tunnel test:













See what I mean? Ram takes first place over and over. Loaded, empty, uphill, on the flats, always fastest.

Is isn't until they test it on the Eisenhower Tunnel grade (same as used by TFLTruck in their "Ike Gauntlet" test) that the Ram was slower. I chalked it up to the fact that it was carrying between 2000# and 3000# more than the GM and Ford because they loaded all the trucks up to 90% of their GCWR and the Ram has a much higher GCWR so it had much more weight.

It appears though, that it was the extra weight AND something to do with the engine programming for high elevations.

Here is the Eisenhower tunnel test done by PUTC:



And the note that followed the description of their Eisenhower tunnel grade towing test:

"How We Did the Testing

We knew we wanted to do something special here, so we opted to run each truck as close to its manufacturer-stated GCWR — meaning all it can carry and tow. Simply put, we wanted to see how well or poorly they performed at their limits. We know most people aren't likely to do this kind of towing (and if they did, they'd probably buy a one-ton dualie turbo-diesel), but how well a pickup does near its limits is likely to say a lot about how well it will do when things aren't so tough.

Our trailer for this event, when empty weighs, about 6,000 pounds but we had two 330-gallon water tanks (each weighing 2,800 pounds) wedged inside, bringing the total weight close to 12,000 pounds, near but not over each truck's stated maximum conventional tow ratings.

The F-250's GCWR is 19,000 pounds; the Chevy's is just more than 20,000 pounds, and the Ram 2500's is just more than 22,000 pounds. We attempted to adjust each max trailer weight by dumping a certain amount of water from each truck or trailer, getting as close as possible to 90 percent of the vehicle's GCWR number."

[Targa]

Didn't he just explain it with the 1st and 2nd gear ratios he posted?

[Bigfoot_affair]

blderman wrote:
Here is a brief example based on trans/rear end gear ratios. I know this isn't proof of anything but it shows the design flaw, in my opinion.

Ram 6.4 (420ft lbs @ 4000 rpm)

1st Gear 3.23= 1,356 ft.lbs x 4.10 rear= 5,559 ft.lbs
2nd Gear 1.84= 772 ft.lbs x 4.10 rear= 3,165 ft.lbs


Chevy 6.0 (380ft.lbs @ 4200rpm)

1st Gear 4.03= 1,531 ft.lbs x 4.10 rear= 6,277 ft.lbs
2nd Gear 2.36= 896 ft.lbs x 4.10 rear= 3,673 ft.lbs


So mathematically speaking the Chevy has 718 ft.lbs more in 1st gear and 508 ft.lbs more in 2nd gear. If my math is correct that is a substantial difference in torque to the rear wheels. If the Ram had the same gear ratios as the Chevy it would have walked away easily.

LOL! So how do you explain the Chevy going up the Ike in second gear? It only shifted into first just before the top of the mountain.

Face it, the Ram 6.4 is all paper #'s and was beat by a engine trans combo that was put into these trucks back in 07.

[blderman]

IdaD wrote:

blderman wrote:

mowin wrote:
How often are you planning on running those 7%+ hills and at those altitudes? So the Ram took a little longer. I would never run my rig with my foot to the floor for that long anyway.

Coming from a 2011 gmc 6.0 with 3:73's, I can safely say my 6.4 Ram with 3:73's easily out tow's my GMC 6.0.

I won't be very often and I am not saying its a bad truck; I am still seriously considering buying one. I just think it was a really bad move on Ram's part to not address the gear spacing. Even the F150 has better gear ratios.

In Oregon you'll deal with those kind of grades reasonably regularly. I'm over in Idaho and will deal with them even more regularly. But in general if you're in the northwest or really the west in general, handling these grades (up and down) is a pretty big factor to consider.

I'm a prospective buyer as well, and all of these 6.4 threads the last few days have really moved my needle back over to the CTD. I really like the current Ram 2500/3500 quite a bit better than the comparable offerings from GM or Ford for various reasons, so I've discarded those options (unless I waited on the 2016 Super Duty, but I don't want to wait that long). I guess that leaves me with the feeling that the CTD is really the best choice for me, even though it costs a little more and might not work quite as well as a short hop daily driver. I had previously decided I'd probably go that way but seeing gas prices drop the last couple of weeks while diesel continues to linger high had made me reconsider it a bit.

Oregon doesn't have too many grades that match the IKE run. Especially not at the same elevation, the highest paved road in Oregon is only 7,400' or so. That being said, I agree with your points. It's making me consider staying in my Ford for awhile longer even though I really, really don't like it. My next step is to go test drive one, I realistically only tow heavy about 20 days a year so it's not like I will be dealing with power issues all the time.

[IdaD]

blderman wrote:

mowin wrote:
How often are you planning on running those 7%+ hills and at those altitudes? So the Ram took a little longer. I would never run my rig with my foot to the floor for that long anyway.

Coming from a 2011 gmc 6.0 with 3:73's, I can safely say my 6.4 Ram with 3:73's easily out tow's my GMC 6.0.

I won't be very often and I am not saying its a bad truck; I am still seriously considering buying one. I just think it was a really bad move on Ram's part to not address the gear spacing. Even the F150 has better gear ratios.

In Oregon you'll deal with those kind of grades reasonably regularly. I'm over in Idaho and will deal with them even more regularly. But in general if you're in the northwest or really the west in general, handling these grades (up and down) is a pretty big factor to consider.

I'm a prospective buyer as well, and all of these 6.4 threads the last few days have really moved my needle back over to the CTD. I really like the current Ram 2500/3500 quite a bit better than the comparable offerings from GM or Ford for various reasons, so I've discarded those options (unless I waited on the 2016 Super Duty, but I don't want to wait that long). I guess that leaves me with the feeling that the CTD is really the best choice for me, even though it costs a little more and might not work quite as well as a short hop daily driver. I had previously decided I'd probably go that way but seeing gas prices drop the last couple of weeks while diesel continues to linger high had made me reconsider it a bit.

[blderman]

katoom400 wrote:

blderman wrote:

mowin wrote:
How often are you planning on running those 7%+ hills and at those altitudes? So the Ram took a little longer. I would never run my rig with my foot to the floor for that long anyway.

Coming from a 2011 gmc 6.0 with 3:73's, I can safely say my 6.4 Ram with 3:73's easily out tow's my GMC 6.0.

I won't be very often and I am not saying its a bad truck; I am still seriously considering buying one. I just think it was a really bad move on Ram's part to not address the gear spacing. Even the F150 has better gear ratios.

Is this the same gear ratio's with the 5.7, if so I would think it would be even worse?

Yes, same ratios with the 5.7. They are a little better than the 65RFE but not much. I think they provide a nice driving experience with not a lot of hunting, but they are less than ideal for heavy towing.

[katoom400]

blderman wrote:

mowin wrote:
How often are you planning on running those 7%+ hills and at those altitudes? So the Ram took a little longer. I would never run my rig with my foot to the floor for that long anyway.

Coming from a 2011 gmc 6.0 with 3:73's, I can safely say my 6.4 Ram with 3:73's easily out tow's my GMC 6.0.

I won't be very often and I am not saying its a bad truck; I am still seriously considering buying one. I just think it was a really bad move on Ram's part to not address the gear spacing. Even the F150 has better gear ratios.

Is this the same gear ratio's with the 5.7, if so I would think it would be even worse?

[blderman]

mowin wrote:
How often are you planning on running those 7%+ hills and at those altitudes? So the Ram took a little longer. I would never run my rig with my foot to the floor for that long anyway.

Coming from a 2011 gmc 6.0 with 3:73's, I can safely say my 6.4 Ram with 3:73's easily out tow's my GMC 6.0.

I won't be very often and I am not saying its a bad truck; I am still seriously considering buying one. I just think it was a really bad move on Ram's part to not address the gear spacing. Even the F150 has better gear ratios.

[mowin]

How often are you planning on running those 7%+ hills and at those altitudes? So the Ram took a little longer. I would never run my rig with my foot to the floor for that long anyway.

Coming from a 2011 gmc 6.0 with 3:73's, I can safely say my 6.4 Ram with 3:73's easily out tow's my GMC 6.0.

[blderman]

Here is a brief example based on trans/rear end gear ratios. I know this isn't proof of anything but it shows the design flaw, in my opinion.

Ram 6.4 (420ft lbs @ 4000 rpm)

1st Gear 3.23= 1,356 ft.lbs x 4.10 rear= 5,559 ft.lbs
2nd Gear 1.84= 772 ft.lbs x 4.10 rear= 3,165 ft.lbs


Chevy 6.0 (380ft.lbs @ 4200rpm)

1st Gear 4.03= 1,531 ft.lbs x 4.10 rear= 6,277 ft.lbs
2nd Gear 2.36= 896 ft.lbs x 4.10 rear= 3,673 ft.lbs


So mathematically speaking the Chevy has 718 ft.lbs more in 1st gear and 508 ft.lbs more in 2nd gear. If my math is correct that is a substantial difference in torque to the rear wheels. If the Ram had the same gear ratios as the Chevy it would have walked away easily.

[blderman]

katoom400 wrote:

blderman wrote:

ib516 wrote:

blderman wrote:
Have you guys watched the Ike Towing Test posted this weekend? I have no idea how credible the testing guys are but I was pretty disappointed in the results. It's making me second guess the 6.4 now. The F150 Ecoboost towing just 1,800lbs less made it up the hill 4 minutes faster than the Ram. It appears the 2nd gear ratio on the 6.4 is really a poor fit for the engine. Thoughts?

You have to read the comment they posted a couple hours ago. They contacted RAM about the results, and got this response:

"We spoke with Ram and here's what they said about the slower Results of this Ike Gauntlet Run: "During the Silverado drive, you spoke negatively of the shift calibration. The tested Chevy was we assume hunting between 1st and 2nd, and ranged from 5300erpm to around 2800erpm, which you didn’t seem to like. The Chevy revved very high up the hill for extended periods of time, over 5000erpm.

Ram Truck “invented” the first gear hold feature – and calibrated it – to avoid gear hunting and driving at excessively high rpm’s.
Ike is a variable grade and we worked hard to develop a calibration that appropriately manages torque on the run and other grades.
We don’t want the truck to rev high for extended periods of time and purposely hold 4,200 rpm.

Bottom line – our truck performed exactly as expected by delivering a more comfortable hauling experience, better vehicle longevity and improved fuel economy. Time to the top of the hill is only one small piece of the driving experience and our engineers take a number of variable into consideration. Ask yourself if just over one minute is worth other negative driver inputs."?

I haven't experienced any limiting in any towing I have done, but then the highest elevation I have been to so far is about 7000'.

That is the response I would expect from an engineer. It's not like they are going to admit that 2nd gear is the wrong ratio. This definitely has my plans on hold till I can do more research. It would be interesting to see how it performs in manual mode.

would you really say 2nd gear is the wrong ratio, or is the shift logic a bit off?

Really, would you allow your truck to climb steep incline like that? I know they had to keep all things as equal as they could for the test, but in the real world, are you going to let the truck slow down to 30mph? No! you are going to manually downshift and let the truck rev! The Chevy was certainly at 5k for long periods of time, and that is most likely why it got to the top faster.

A more accurate test would have been to set points along the route where you designate down shifts for both trucks and see how they fair. the fact that the Ram held second for far too long doesn't bother me because I would never have let that happen in the real world.

IMO the only thing you could knock the Ram for is failure to downshift on an tough grade. BIG DEAL!

oh, one more thing for the guys bashing the Ram, watch the Chevy video @ 19:45 they start talking about how the truck should have downshifted and is holding the gear for way to long and they are down to 35mph.

So I would say if you have no clue know how to drive a truck pulling a heavy trailer, you would be better served buying a Chevy as it will downshift for you in case you fell asleep.

and no I'm not a RAM lover, I'm a Tundra guy looking at all the options for my next truck and I really think all of the big 3 are so close you just have to pick the one that appeals to you or fits your needs the most and you can't go wrong.

I want to first say that I am not bashing the Ram. My only hesitation is that I am moving from a diesel back to gas and I really thought this engine was going to perform better. Not saying it's a bad truck, I know it is WAY better than my current Ford and I look forward to being in a Ram truck again very soon.

Yes, I do believe the 2nd gear is too high. The ratio spread between 1st and 2nd is pretty large, with the Cummins it is able to power its way through due to the huge torque curve. The 6.4 cannot and that is why it slowly lost speed till it dropped back into 1st. If the engineers really programmed it to stay in first and limit it to 4,200rpm during extended heavy loads I think they made a huge mistake. I really hope that manual mode can override that feature. With stated power of the 6.4 it should have been able to handle that grade with relative ease compared to the Chevy 6.0.