3:21 vs 3:92 Gears

[bucolic]

I just traded my 2019 Laramie 5.7 Hemi with 3.21 gears for a 2021 Limited Etourque Hemi with 3.92 gears. Prior to the 2019 Laramie, I had a 2016 Ram Big Horn Hemi with 3.21 gears. I put 81K on the 2016 Big Horn and I put 28K on the 2019 Laramie so I have over 100K miles driving with the 3.21 in a short period of time. I towed a 6000lb trailer this summer with the Laramie 3.21's a total of 8000 miles. I did a cross country trip from NY to CA and back towing the trailer. It was not effortless. I felt under trucked the whole trip. The 3.21's get the camper going no problem at all. The trouble comes in with wind and hills. It could comfortably pull much heavier loads if they did not have the large sail the camper creates. Of course, towing a camper with the light-duty 1/2 ton is not ideal and most people who tow a lot bump up to the 3/4 cummings but I did;t want to deal with a 3/4 ton truck or the diesel. I think the Laramie was rated at 7500 lbs towing capacity where the Limited with the 3.92 is rated at about 11,000 lbs.

Now, I'll touch on the biggest reason I traded. The 26-gallon tank. It was miserable. Range while towing was 250 miles when filled so every 150 miles you needed to start looking for a gas station. Especially in rural areas like Utah and such. On days I did 600 miles I was stopping as much as 4 times to fill up. Range anxiety was like being in an electric car LOL. I needed the 33-gallon tank and decided to get the 3.92 gears as well. At this time I will also mention something I was not aware of and that is that many of the Hemi's with Etourque come with a 23-gallon tank. I just can't even imagine towing with that small a tank so when looking at these trucks be aware of that. Someone correct me if I am wrong. Even for everyday driving, 23 gallons seems absurd on these trucks.

So, back to the 3.92 gears. Having driven over 100k miles with the 3.21's I can say from experience I can feel the difference with the 3.92's. I have yet to tow with it so I can't comment on that yet. But in everyday driving the difference is substantial. The truck shifts faster and going up hills it just goes up them. The 3.21's would shift down into 6th or even 5th without a load on hills and the 3.92's just stayed right there in 7th or 8th gear. It runs at about 1800-1900 RPMs at 65-70 whereas the 3.21's appeared to be right around 1500 RPMs so noticeable difference there. My mileage is way off what others say but the truck only has 600 miles on it so perhaps that will climb. I could get 20-21 mpg with the 3.21's and the 3.92 so far have never been higher than 17. The 3.21's seem to be lugging compared to the 3.92's but the lower RPMs are noticeable on the 3.21's. I can see the benefits of both. I don't expect to see a substantial difference when towing with the 3.92's but I am hoping it's enough to take the edge off in the wind and hills. Overall I think the 3.21's give a nicer casual driving experience. Smooth, low rpm's and not as quick shifting. The 3.92's have snappier, quicker feeling shifts. They also go into eco mode more often at lower speeds than the 3.21's. The 33-gallon tank though is what I am most excited about! I can't stress enough how miserable that small tank was on my trip. I swear I spent more time at gas stations than I did at the campgrounds! If I bought one of these and found out it only had a 23-gallon tank I would have been beside myself.

So looking forward to seeing if the higher gears take the edge off of towing my camper. Even if they don't I am sure I will enjoy the added features of the Limited over the Laramie and the 33-gallon tank.

 

[BigD]

I just traded my 2019 Laramie 5.7 Hemi with 3.21 gears for a 2021 Limited Etourque Hemi with 3.92 gears. Prior to the 2019 Laramie, I had a 2016 Ram Big Horn Hemi with 3.21 gears. I put 81K on the 2016 Big Horn and I put 28K on the 2019 Laramie so I have over 100K miles driving with the 3.21 in a short period of time. I towed a 6000lb trailer this summer with the Laramie 3.21's a total of 8000 miles. I did a cross country trip from NY to CA and back towing the trailer. It was not effortless. I felt under trucked the whole trip. The 3.21's get the camper going no problem at all. The trouble comes in with wind and hills. It could comfortably pull much heavier loads if they did not have the large sail the camper creates. Of course, towing a camper with the light-duty 1/2 ton is not ideal and most people who tow a lot bump up to the 3/4 cummings but I did;t want to deal with a 3/4 ton truck or the diesel. I think the Laramie was rated at 7500 lbs towing capacity where the Limited with the 3.92 is rated at about 11,000 lbs.

Now, I'll touch on the biggest reason I traded. The 26-gallon tank. It was miserable. Range while towing was 250 miles when filled so every 150 miles you needed to start looking for a gas station. Especially in rural areas like Utah and such. On days I did 600 miles I was stopping as much as 4 times to fill up. Range anxiety was like being in an electric car LOL. I needed the 33-gallon tank and decided to get the 3.92 gears as well. At this time I will also mention something I was not aware of and that is that many of the Hemi's with Etourque come with a 23-gallon tank. I just can't even imagine towing with that small a tank so when looking at these trucks be aware of that. Someone correct me if I am wrong. Even for everyday driving, 23 gallons seems absurd on these trucks.

So, back to the 3.92 gears. Having driven over 100k miles with the 3.21's I can say from experience I can feel the difference with the 3.92's. I have yet to tow with it so I can't comment on that yet. But in everyday driving the difference is substantial. The truck shifts faster and going up hills it just goes up them. The 3.21's would shift down into 6th or even 5th without a load on hills and the 3.92's just stayed right there in 7th or 8th gear. It runs at about 1800-1900 RPMs at 65-70 whereas the 3.21's appeared to be right around 1500 RPMs so noticeable difference there. My mileage is way off what others say but the truck only has 600 miles on it so perhaps that will climb. I could get 20-21 mpg with the 3.21's and the 3.92 so far have never been higher than 17. The 3.21's seem to be lugging compared to the 3.92's but the lower RPMs are noticeable on the 3.21's. I can see the benefits of both. I don't expect to see a substantial difference when towing with the 3.92's but I am hoping it's enough to take the edge off in the wind and hills. Overall I think the 3.21's give a nicer casual driving experience. Smooth, low rpm's and not as quick shifting. The 3.92's have snappier, quicker feeling shifts. They also go into eco mode more often at lower speeds than the 3.21's. The 33-gallon tank though is what I am most excited about! I can't stress enough how miserable that small tank was on my trip. I swear I spent more time at gas stations than I did at the campgrounds! If I bought one of these and found out it only had a 23-gallon tank I would have been beside myself.

So looking forward to seeing if the higher gears take the edge off of towing my camper. Even if they don't I am sure I will enjoy the added features of the Limited over the Laramie and the 33-gallon tank.

What's your RPM at when towing that 6,000 lbs trailer. I was towing about that much yesterday & I was around 2,400 RPM at 70 mph with the 3.92 gears. Seems like that'd be hard on the motor over a long time. Without a trailer I'm still right around 2,000 RPM at 70 mph. Also, I went thru about 1/2 tank of gas towing 100 miles yesterday with that 23 gallon tank !!

 

[Zig10]

What's your RPM at when towing that 6,000 lbs trailer. I was towing about that much yesterday & I was around 2,400 RPM at 70 mph with the 3.92 gears. Seems like that'd be hard on the motor over a long time. Without a trailer I'm still right around 2,000 RPM at 70 mph. Also, I went thru about 1/2 tank of gas towing 100 miles yesterday with that 23 gallon tank !!

I don't think it's all that hard on the motor. That RPM range isn't exactly high revs for this engine, and it keeps you in the powerband while towing. With my boat (7500 lbs) at highway speed I get 8-9 MPG, which exactly matches what I get in my '18 Expedition with the EcoBoost V6...which matches what I was getting in my '16 Yukon with the 5.3. Towing a decent load at speed just sucks up fuel no matter what gas engine you're running.

I guess if you want good mileage in any of these vehicles, particularly while towing, you need the diesel.

 

[Scram1500]

What's your RPM at when towing that 6,000 lbs trailer. I was towing about that much yesterday & I was around 2,400 RPM at 70 mph with the 3.92 gears. Seems like that'd be hard on the motor over a long time. Without a trailer I'm still right around 2,000 RPM at 70 mph. Also, I went thru about 1/2 tank of gas towing 100 miles yesterday with that 23 gallon tank !!

The Hemi is a high revving V8, it can sit at 4000 rpm all day long. 2400 rpm is not much at all

 

[BigD]

The Hemi is a high revving V8, it can sit at 4000 rpm all day long. 2400 rpm is not much at all

Good to know. Thanks. She sure likes to suck down the gas at those RPM's though. I see why if u tow often you'd want the diesel. Definitely worth the extra $5,000 if towing a lot.

 

[redneck]

I don't think it's all that hard on the motor. That RPM range isn't exactly high revs for this engine, and it keeps you in the powerband while towing. With my boat (7500 lbs) at highway speed I get 8-9 MPG, which exactly matches what I get in my '18 Expedition with the EcoBoost V6...which matches what I was getting in my '16 Yukon with the 5.3. Towing a decent load at speed just sucks up fuel no matter what gas engine you're running.

I guess if you want good mileage in any of these vehicles, particularly while towing, you need the diesel.

8-9 mpg is not good i have a 2017 gmc with the 6.2 motor & 3.21 gears i tow my very tall box trailer total weight 7600# and my gmc will get 13.6 at 72mph been doing this for 4 years. unloaded its closer to the rams mpg 82mph i get 20.2 on trips & 16 in town

 

[silver billet]

The 3.21's would shift down into 6th or even 5th without a load on hills and the 3.92's just stayed right there in 7th or 8th gear. It runs at about 1800-1900 RPMs at 65-70 whereas the 3.21's appeared to be right around 1500 RPMs so noticeable difference there.

This transmission and 2 rear ends match up so perfectly, that it's physically impossible for you to have a noticable/signifcant difference out on the highway (with one exception). Yes you might be in 6th instead of 7th, but that's just the "label". The actual gear ratio in use will be approximately equal (3.21 for the 3.21, and 3.2144 for the 3.92).

Now if you're driving at 70 mph, yes you will notice a difference there, because the 3.21 has the higher final gear ratio. But keep in mind if you're towing, the 3.21 will never tow anything significant in 8th, so it will use the same 5 gear ratios on the highway that the 3.92 has available.

 

[Ramtruck86]

I don't think it's all that hard on the motor. That RPM range isn't exactly high revs for this engine, and it keeps you in the powerband while towing. With my boat (7500 lbs) at highway speed I get 8-9 MPG,

If you are regularly towing that much I would definetly consider a diesel or more likely a 2500/3500. You having a limited could be good trade in maybe get into a Laramie cummins at decent price.

 

[Zig10]

If you are regularly towing that much I would definetly consider a diesel or more likely a 2500/3500. You having a limited could be good trade in maybe get into a Laramie cummins at decent price.

It's not often enough to push me to a 2500 or a diesel, fortunately. 2-3 longish trips per year.

 

[bucolic]

This transmission and 2 rear ends match up so perfectly, that it's physically impossible for you to have a noticable/signifcant difference out on the highway (with one exception). Yes you might be in 6th instead of 7th, but that's just the "label". The actual gear ratio in use will be approximately equal (3.21 for the 3.21, and 3.2144 for the 3.92).

Now if you're driving at 70 mph, yes you will notice a difference there, because the 3.21 has the higher final gear ratio. But keep in mind if you're towing, the 3.21 will never tow anything significant in 8th, so it will use the same 5 gear ratios on the highway that the 3.92 has available.

Makes sense. I take it you will lose one lower gear on the 3.21? Is that where the increased tow capacity comes in? It is a significant difference between the two. I am taking it the increased tow capacity might be all smoke and mirrors and the 3.92 can just get more weight going than the 3.21's? At highway speeds with that large sail created by the camper I won't notice any difference?

 

[Dusty1948]

This transmission and 2 rear ends match up so perfectly, that it's physically impossible for you to have a noticable/signifcant difference out on the highway (with one exception). Yes you might be in 6th instead of 7th, but that's just the "label". The actual gear ratio in use will be approximately equal (3.21 for the 3.21, and 3.2144 for the 3.92).

Now if you're driving at 70 mph, yes you will notice a difference there, because the 3.21 has the higher final gear ratio. But keep in mind if you're towing, the 3.21 will never tow anything significant in 8th, so it will use the same 5 gear ratios on the highway that the 3.92 has available.

Since I've had both the 3.92 and now a 3.21 axle, I concur. My current '19 with the 3.21 tows my 6,100 lb. tractor and trailer with ease, and actually has less gear hunting on the hills on I-390 just south of Dansville, NY. With my previous truck (3.92s) the 8-speed would shift back-and-forth between gears on the same hills towing approx. 9300 lbs.

NOTE: The gear ratios are slightly different between the 8HP70 I had in the 2014 and the 8HP75 in my 2019.

Regards,
Dusty
2019 Ram 1500 Billet Silver Laramie Quad Cab 2WD, 5.7 Hemi, 8HP75, 3.21 axle, 33 gallon fuel tank, factory dual exhaust, 18” wheels. Build date: 03 June 2018. Now at: 045590 miles.

 

[hunter1234]

I have the 3.21 on a 2020 eco diesel. Tow regularly but only a loaded 3-4 thousand pound utility trailer. Never an issue pulling up, down or straight. I do a lot more long mile commuter driving (150 mile work commute each day) and like the MPG I get with the 3.21 - though to be honest not sure what I would see with a 3.92. I figure if I move up to an RV pushing 7-9 thousand pounds it will force me to move to a 2500 Would want the HD truck for that and my feeling of security.

 

[silver billet]

Makes sense. I take it you will lose one lower gear on the 3.21? Is that where the increased tow capacity comes in? It is a significant difference between the two. I am taking it the increased tow capacity might be all smoke and mirrors and the 3.92 can just get more weight going than the 3.21's? At highway speeds with that large sail created by the camper I won't notice any difference?

The very lowest gears are different as well, so yes that's where the increase in tow rating comes from. 3.92 will always pull harder from a stop than the 3.21 can. So I'm not saying "it's smoke and mirrors"; the difference is real, but you have to consider everything, not just 1 specific metric.

• 3.92 will pull harder from a dead stop, always
• Once the 3.21 is in third; at that speed (mph) the 2 trucks are equivalent for towing, the remaining 5 gears you would use for city/highway towing have almost identical gear ratios
• 3.21 has one final gear ratio the 3.92 doesn't have; for towing its irrelevant (can't tow in 8th anyway), for unloaded commuting it is a significant savings in gas
• more than likely: your truck is payload limited, not tow limited. Most trucks have a payload around 1300 to 1500 pounds, regardless of axle ratio, so when you add up your cargo, family, tongue weight etc, you can't realistically/safely tow > 8000 pounds anyway because the truck would be carrying more weight than you are allowed to carry.
• You can drop a 707 hp hellcat into the engine bay and upgrade to 6.10 rear gear ratio for all I care, but you still can't tow more than 8000 pounds due to payload
• if you plan to off road or install larger tires, the 3.92 is very worth considering

So in my opinion: if your truck stays on road, pulls <= 7000 pounds once in a while on a summer trip here and there, the 3.21 is perfect. If you're pulling 8000+, well, you could try squeezing that out of the 1500 by buying a stripped down truck to keep your payload up and then get the 3.92, but a better option (my opinion) would be to upgrade to a 2500. 8000 pounds is definitely 3/4 ton territory.

 

[BowDown]

This transmission and 2 rear ends match up so perfectly, that it's physically impossible for you to have a noticable/signifcant difference out on the highway (with one exception). Yes you might be in 6th instead of 7th, but that's just the "label". The actual gear ratio in use will be approximately equal (3.21 for the 3.21, and 3.2144 for the 3.92).

Now if you're driving at 70 mph, yes you will notice a difference there, because the 3.21 has the higher final gear ratio. But keep in mind if you're towing, the 3.21 will never tow anything significant in 8th, so it will use the same 5 gear ratios on the highway that the 3.92 has available.

Seems like a lot of people miss this fact; 3.21 in 7th gear on the hwy is the same ratio as the 3.92 in 8th

 

[Dusty1948]

Seems like a lot of people miss this fact; 3.21 in 7th gear on the hwy is the same ratio as the 3.92 in 8th

Of course, this begs the question, why does the 3.92 axle increase towing to 11,000+ over the 3.21?

Best regards,
Dusty
2019 Ram 1500 Billet Silver Laramie Quad Cab 2WD, 5.7 Hemi, 8HP75, 3.21 axle, 33 gallon fuel tank, factory dual exhaust, 18” wheels. Build date: 03 June 2018. Now at: 045590 miles.

 

[JJRamTX]

The majority of us that tow often want 3 things. 33 Gal Tank, 3.92 and eTorque. The 3.92 and eTorque really allow you to tow 10,000 Lbs+ and the reason to get the 3.92 is Spider gears, pinion, and Diff Gears and the wear they will have towing heavy with a 3.21. You trade capability for fuel economy. I tow heavy quite often so it was no choice and I am very happy with my fuel economy since my last Ram got 2 MPG less overall. **Boat is my Heavy**

 

[BowDown]

Of course, this begs the question, why does the 3.92 axle increase towing to 11,000+ over the 3.21?

Best regards,
Dusty
2019 Ram 1500 Billet Silver Laramie Quad Cab 2WD, 5.7 Hemi, 8HP75, 3.21 axle, 33 gallon fuel tank, factory dual exhaust, 18” wheels. Build date: 03 June 2018. Now at: 045590 miles.

I'd guess its the initial drivetrain load from a standing start. 3.92 would reduce that drivetrain "strain" over the 3.21 and at max weight, that strain may be too much for the driveline components over time in a 3.21 truck.

 

[Zig10]

8-9 mpg is not good i have a 2017 gmc with the 6.2 motor & 3.21 gears i tow my very tall box trailer total weight 7600# and my gmc will get 13.6 at 72mph been doing this for 4 years. unloaded its closer to the rams mpg 82mph i get 20.2 on trips & 16 in town

6.2 had a way better torque curve than the 5.3 and was definitely the better towing motor. That said, the hard top on my boat with the radar on top basically becomes a hard parachute at speed. My previous boat did not have the hard top and was only a little lighter, and I saw an extra 2 MPG with that one.

 

[Dusty1948]

6.2 had a way better torque curve than the 5.3 and was definitely the better towing motor. That said, the hard top on my boat with the radar on top basically becomes a hard parachute at speed. My previous boat did not have the hard top and was only a little lighter, and I saw an extra 2 MPG with that one.

If you look at the Torque/HP curves for the GM 6.2 and the 5.7 Hemi, it's really remarkable how close they really are. On both engines torque and horsepower cross at just about the same 4100 RPM. The 5.7 actually delivers its peak torque at about 3950 and the GM 6.2 at about 4200. In the low RPM range (1000 RPM) the 5.7 Hemi starts producing horsepower and torque just a little bit sooner. At 1500 RPM the 6.2 is about 25 lb. ft. ahead of the 5.7 Hemi. The 6.2 has a flatter torque curve. Across the RPM range the GM 6.2 is never more than <>35 lb. ft. torque ahead of the 5.7 according to published engine graphs. So the advantage of the GM 6.2 motor is really the result of its raw larger displacement of 0.5L.

Best regards,
Dusty
2019 Ram 1500 Billet Silver Laramie Quad Cab 2WD, 5.7 Hemi, 8HP75, 3.21 axle, 33 gallon fuel tank, factory dual exhaust, 18” wheels. Build date: 03 June 2018. Now at: 045634 miles.

 

[Zig10]

If you look at the Torque/HP curves for the GM 6.2 and the 5.7 Hemi, it's really remarkable how close they really are. On both engines torque and horsepower cross at just about the same 4100 RPM. The 5.7 actually delivers its peak torque at about 3950 and the GM 6.2 at about 4200. In the low RPM range (1000 RPM) the 5.7 Hemi starts producing horsepower and torque just a little bit sooner. At 1500 RPM the 6.2 is about 25 lb. ft. ahead of the 5.7 Hemi. The 6.2 has a flatter torque curve. Across the RPM range the GM 6.2 is never more than <>35 lb. ft. torque ahead of the 5.7 according to published engine graphs. So the advantage of the GM 6.2 motor is really the result of its raw larger displacement of 0.5L.

Best regards,
Dusty
2019 Ram 1500 Billet Silver Laramie Quad Cab 2WD, 5.7 Hemi, 8HP75, 3.21 axle, 33 gallon fuel tank, factory dual exhaust, 18” wheels. Build date: 03 June 2018. Now at: 045634 miles.

I agree. I was comparing the 6.2 to my old 5.3, not the Hemi. Sorry for the confusion there...