Axle Ratio

[CanuckRam1313]

As all have said...higher RPM's are fine with our trucks!

But, keeping temps in the engine and transmission down are crucial for longevity and dependability.

If you have higher mileage in your truck, perhaps do a coolant flush and fill and a new t-stat.
Use a great quality 5W30 synthetic oil and great quality oil filter.
Perhaps consider a transmission fluid and filter service, AND, put in the "caulk04" transmission cooler bypass upgrade to keep those transmission temps down.
Maybe a spark plug change, too?

 

[Wild one]

Thank you for responding. Looks like I'm ok. I DO use the tow/haul mode. I'll just let it rev and do it's thing. I thought I was hurting the engine at those high revs at 70mph. I'll do 65 and be happy and have more $ in my pocket!
However, for some reason, I really thought the 3.92 ratio would help lower the rpm's. I've also been reading about the new Etorque 5.7. I'll continue to educate myself. Thanks to all.

You must be younger,lol. Back in the earlier days before overdrive transmissions it was pretty common for vehicles to be running at 3,000+ rpm at 60 mph

The 3.21 and 3.92 is very commonly misunderstood, if you research you'll find many making false assumptions and claims about this. A large part of the misunderstanding is probably due to the GCWR between the two trucks. If the only difference is gear ratio, the 3.92 is "rated" to tow almost 3000 pounds more.

However that rating is based on many factors, one of them being 0 - 30 mph and 0 - 60 mph acceleration tests. The 3.92 will accelerate faster from a stop when you mash the pedal, no question. That's why the 3000 pound rating difference is there.

However, in my experience I never mash the pedal from a stop while towing. I never need more power from a stop, I need more power on the onramps, or passing a semi up a hill on the freeway. At that point the same gear ratios are available in both trucks, the transmission will shift you where you need to be and the experience will be 100% identical in both trucks.

Many will talk about "increased torque in every gear", which is true, but they miss the fact that the two trucks aren't in the same gear number at the same time, once you're rolling past 2'nd the 3.92 will usually be ahead one numerical gear which means they end up using the same gear ratio with the same amount of torque multiplication at the wheels.

In other words: "gear number" is not equal to "gear ratio". gear number is unimportant, gear ratio is what counts, and there 5 to 6 almost identical gear ratios shared between both trucks.

Final drive ratio,are the words your looking for,lol.Which is transmission ratio multiplied by rearend ratio

 

[ramffml]

Final drive ratio,are the words your looking for,lol.Which is transmission ratio multiplied by rearend ratio

Yep but I've found it confusing in the past to write it like that since some think the "final" refers to "last gear" (ie "8th gear ratio" in the case of our rams).

 

[Ratman6161]

I own a 2019 1500 Laramie Crew Cab. 5.7 HEMI 3.21 axle ratio. It pulled my old camper like a dream at 3050 pounds. My NEW travel trailer is 4500 pounds unloaded, dual axle. I don't load it up. I travel pretty light. The issue I have is with high RPM'S. Seems I have to crawl on the highway at 60mph or hit 3500 rpms or MORE on hills. It's not "comfortable" to me. The truck struggles. I'm thinking about trading trucks. I'm looking for a 2500 gas but I don't want to break the bank. They are hard to come by. I'm wondering if I choose a 1500 with a 5.7 and a 3.92 axle ratio. Will it help to reduce rpms? I don't want to fly down the road but sometimes I like to drive the speed limit, 68 or 70.
Much appreciated. BTW, I've owned this truck for 2.5 years and I LOVE it. The Harmon Kardon is the DEAL. This is my 4th RAM
Thank you

On thing I'll comment on is where you say "I'm looking for a 2500 gas ". Engine wise, the 6.4 in the 2500 isn't massively more powerfull than the 5.7 and makes its peak torque at 4000 RPM. So it's going to rev too. I don't co sidereal this a problem.

On my 2500 I was debating between 5he 3.73 and the 4.10. I actually built a spreadsheet that calculated the final drive ratio in each transmission gear and c9mbined with the tire size I can calculate the engine RPM for a given speed (I admit it, I like math). With my previous truckmwith the 4.10, on level ground and calm winds AT 70 MPH I'd be in 7th when towing my travel trailer. That equates to 2422 RPM. Same conditions with the new truck and 3.73 I'm predicting it will be 2203, or nearly the same. But at a slightly higher RPM, the 4.10 truck would be more likely to stay in the higher gear if the headwind picks up for example. So if the 3.73 truck has to downshift to 6th, it's RPM would increase to 2623. So theoretically when the conditions are just right, the 4.10 could potentialy be running at a LOWER RPM. But in reality they are so close it probably makes little difference. There may be a bigger difference on a 1500 because 3.92 -3.21 = .71 where on the 2500 4.10 - 3.73 = .37. But either way, gas engines will rev to an RPM where they are making enough power for the conditions

 

[gwilburn]

I own a 2019 1500 Laramie Crew Cab. 5.7 HEMI 3.21 axle ratio. It pulled my old camper like a dream at 3050 pounds. My NEW travel trailer is 4500 pounds unloaded, dual axle. I don't load it up. I travel pretty light. The issue I have is with high RPM'S. Seems I have to crawl on the highway at 60mph or hit 3500 rpms or MORE on hills. It's not "comfortable" to me. The truck struggles. I'm thinking about trading trucks. I'm looking for a 2500 gas but I don't want to break the bank. They are hard to come by. I'm wondering if I choose a 1500 with a 5.7 and a 3.92 axle ratio. Will it help to reduce rpms? I don't want to fly down the road but sometimes I like to drive the speed limit, 68 or 70.
Much appreciated. BTW, I've owned this truck for 2.5 years and I LOVE it. The Harmon Kardon is the DEAL. This is my 4th RAM
Thank you

My 2014 1500 Laramie Crew has 3.92... it has 97,000. According to the computer, I've pulled my trailer almost 25,000 of those. It's very similar... 28', 102" wide, and 6' inside height. Loaded it's very close to 5000 lbs. Where I live I'm pulling long hills (Ford tests their trucks here).
Like others have said, the higher RPM's are normal for pulling hills (3500 is nothing). Most of my miles are actually over the PA/OH Turnpike and I75 up through Michigan. I run 70-80 mph while towing - usually in 7th gear. It will drop to 6th gear with a headwind or hill. Sometimes 5th gear pulling Laurel Summit on the PA tpk.
I've often wondered if I could "get away with" the 3.21 gears instead of the 3.92. Sure, the same gear ratios work out mathematically, but lower gears (slower rear) allow the same transmission to pull more without undo strain.
Since I live in the mountains (of the East) and pull quite a bit, I opted for the slower rear end. Dad has the 3.21s and doesn't pull anything. FWIW, we get nearly identical MPGs.
This is a good article.

How to Choose the Right Axle Ratio for Your Pickup Truck | Edmunds

If you're going to tow trailers or haul heavy loads, you should understand axle ratios and how they affect performance and fuel economy.

www.edmunds.com

 

[JerryETX]

Your other options are 2500 with 6.4 but to be honest it doesn't have that much power over the 5.7 and the 2500 is quite a bit heavier as well.

This is false! The 6.4 Hemi in a 2500 has considerably more towing power than its little brother. I have a good friend who pulls roughly a 10k lbs moving trailer frequently with his Ram 2500 5.7 Hemi. I have also pulled his trailer with him riding in my truck. We both agreed there’s a considerable difference between the two engines in terms of towing power. Now in terms of get up and go power yeah but the post is about towing power.

 

[ASPLR]

My 2014 1500 Laramie Crew has 3.92... it has 97,000. According to the computer, I've pulled my trailer almost 25,000 of those. It's very similar... 28', 102" wide, and 6' inside height. Loaded it's very close to 5000 lbs. Where I live I'm pulling long hills (Ford tests their trucks here).
Like others have said, the higher RPM's are normal for pulling hills (3500 is nothing). Most of my miles are actually over the PA/OH Turnpike and I75 up through Michigan. I run 70-80 mph while towing - usually in 7th gear. It will drop to 6th gear with a headwind or hill. Sometimes 5th gear pulling Laurel Summit on the PA tpk.
I've often wondered if I could "get away with" the 3.21 gears instead of the 3.92. Sure, the same gear ratios work out mathematically, but lower gears (slower rear) allow the same transmission to pull more without undo strain.
Since I live in the mountains (of the East) and pull quite a bit, I opted for the slower rear end. Dad has the 3.21s and doesn't pull anything. FWIW, we get nearly identical MPGs.
This is a good article.

How to Choose the Right Axle Ratio for Your Pickup Truck | Edmunds

If you're going to tow trailers or haul heavy loads, you should understand axle ratios and how they affect performance and fuel economy.

www.edmunds.com

Great article. Now, I'm thinking I may be better off with a 1500 Ram with 3.92 vs a bulky 2500 since it's my daily driver. My concern is more "comfortable" towing vs the mpg's. Thank you.

 

[farout75]

I own a 2019 1500 Laramie Crew Cab. 5.7 HEMI 3.21 axle ratio. It pulled my old camper like a dream at 3050 pounds. My NEW travel trailer is 4500 pounds unloaded, dual axle. I don't load it up. I travel pretty light. The issue I have is with high RPM'S. Seems I have to crawl on the highway at 60mph or hit 3500 rpms or MORE on hills. It's not "comfortable" to me. The truck struggles. I'm thinking about trading trucks. I'm looking for a 2500 gas but I don't want to break the bank. They are hard to come by. I'm wondering if I choose a 1500 with a 5.7 and a 3.92 axle ratio. Will it help to reduce rpms? I don't want to fly down the road but sometimes I like to drive the speed limit, 68 or 70.
Much appreciated. BTW, I've owned this truck for 2.5 years and I LOVE it. The Harmon Kardon is the DEAL. This is my 4th RAM
Thank you

MY 17 has the 3:92 gear Ratio. I have pulled much more than than 5,000 lbs and hardly noticed it. This was in the mountains and hills. If I were you use your gear selector or the TOW HAUL modes, You should do fine. The 3:21 does help with MPG by 2 to 3 mpg. So I would work with what you have.

 

[farout75]

Thank you for responding. Looks like I'm ok. I DO use the tow/haul mode. I'll just let it rev and do it's thing. I thought I was hurting the engine at those high revs at 70mph. I'll do 65 and be happy and have more $ in my pocket!
However, for some reason, I really thought the 3.92 ratio would help lower the rpm's. I've also been reading about the new Etorque 5.7. I'll continue to educate myself. Thanks to all.

That 48 volt battery system is a real expensive thing to repair. It's a generator not an alternator, and repair will cost a bunch. I believe in keeping it simple.

 

[CaptOchs]

I have a '13 Big Horn 1500 with the 5.7 & 3.92 axle. Tow capacity with my configuration is 10,050 lbs. My new trailer is 7000# empty and 35ft long. So figure somewhere in the 8000-8500 all packed up for camping. I always use tow/haul mode. Once I get going on the expressway I try and keep it around 63-66mph. Generally my RPMs are around 2300-2600 at that speed. I find my RPMs tend to be 100-200 lower if I use cruise control and let the truck maintain speed. I played around with it last summer while towing. Kind of surprising no matter how I babied the pedal I couldn't match the RPMs cruise gave me on the same highway maintaining the same speed.

A sustained 3500 rpm seems high and concerning for a 4500 lb trailer. My trailer is twice as heavy and I hit a sustained 4000 rpms only once. I was climbing a long steep grade for 8 miles. My engine oil temperature jumped 10 degrees and coolant was about 5 degrees higher. I hit the bottom of that hill with everything I could muster at 72 mph. By the time I got to the top I was barely hanging on at 50 mph. Normally, I only hit 3500 or 4000 rpms for short periods passing or larger hills. Most hills it doesn't seem to affect the RPMs much beyond 2600 at expressway speed.

I've had a 5000 lb camper before. What you're experiencing is not normal in my opinion and you are correct to reevaluate your truck. I don't believe you are in 2500 territory, but you are starting to approach a weight class that requires a heavy duty tow package.