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Axle ratio

I was looking into a gear swap just to accommodate larger tires. Figured it would be as easy as a Jeep. I was quoted 2700 in parts, 700 in labor. More than I expected, but not bad since the dealership guaranteed me my warranty would not be affected. I by no means claim to be an expert on warranties since this is my first brand new vehicle.

The problem I had was they can’t tell me for sure if they can reprogram the new gears into the truck. He said I might need to buy a programmer to change my tire size and gear ratio.
 
Cmoar said:
I was looking into a gear swap just to accommodate larger tires. Figured it would be as easy as a Jeep. I was quoted 2700 in parts, 700 in labor. More than I expected, but not bad since the dealership guaranteed me my warranty would not be affected. I by no means claim to be an expert on warranties since this is my first brand new vehicle.

The problem I had was they can’t tell me for sure if they can reprogram the new gears into the truck. He said I might need to buy a programmer to change my tire size and gear ratio.
Click to expand...

Get a Pulsar and you won’t need new gears. It turns the truck into a rocket.
 
Jordan2929 said:
There was a thread a few weeks ago showing the differences of a 3.21 truck and a 3.92 truck. They tested 0-60 loaded and unloaded and the restuls were incredibly similar, like within a couple tenths of a second. This is most likely due to the 8 speed transmission being able to stay in the power band much better than a 6 speed could.

Edit: I found the thread- https://5thgenrams.com/community/threads/3-92-vs-3-21-who-wins-trucktrend-data-shows.5750/
Click to expand...
Performance times have nothing to do with how much weight a truck can tow. You’re comparing apples to oranges.
 
lambone said:
Way underwater on all of it. Don’t be like me...
Click to expand...

That is REALLY great advice, you touched on some EXCELLENT points that many prolly never counted on experiencing UNTIL the ink is dry..

We also have been there MANY many times,... If we added up all the costs for how many times we THOUGHT a better setup on a certain RV or truck we bought would be perfect, only to find some "molehill" in the new setup that grew into a "mountain" causing us back to switching trucks/rv's in search of the perfect "combo"....

For some, they luck out purchasing the perfect setup first time around, but for us, reaching the sweet spot of truck/RV trailer has been extremely costly. We finally wound up with TWO (2) 2019 Ram1500's Daily Drivers (one with 3.92 gears, one with 3.21) AND kept our 2016 2500 Diesel for pulling... Our RV weighs 7500lbs, but like that other poster said, pulling it with our 2500 vs the 2019 (and even WITH the 3.92 gears is a night and day difference)

So yes, NOW we have the perfect setup, but if we could go backwards and do it ALL over again, would prolly just get a 5000 lb camper and just, "suck it up" if the RV didn't have "every single feature we wanted"...

Don't even get me started that having the longer & heavier 2000 lbs and 10 extra feet made us decide to pour concrete all the way around back of house to keep the RV monster out of driveway ($$$$)...(so with the 3 RV trade-ins and multiple switching of trucks would prolly have an extra 60-100K more towards our retirement AND a much nicer house : )

(and it might even be way MORE than that but we're staying on the low end of our estimate so we won't kick ourselves TOO hard :)


rv pull resized.jpg

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driveway2.jpg
 
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3.92 is to tall of a gear for a highway warrior who exceeds 75 mph for more than 80% of your drive and you are planning to keep stock tires. I have driven both trucks with both ratios and have been a mechanic since I could hold a wrench. The comparisons done on these vehicles are not apples to apples. If you plan to change tire size or ply and add the weight or height you won’t have any regrets with 3.92. These trucks are designed to get the best fuel economy and will shift to keep the lowest rpm for the current tires, weight and wind drag. I had a 2016 ecodiesel and added 275 nit to tires that increased ply and weight and it shifted between 7th and 8th on the highway like a gas engine. Most of us buy a diesel for the torque and we don’t like the constant shifting. The 392 gears will provide less friction, heat, power train wear, and More gcw on the door sticker with minimum mileage difference. I will run 35” tires with 392 and will result close to old 3.73 configuration. I have read tons of post on this and I have not read one that someon said the regretted the 3.92. With that being said if I plan to run 32 pound stock Goodyear tires I would use 3.55 ratio. the 3.92 will transition mds better and more often. This is just my opinion so have a great day.....
 
FDXGUY said:
Performance times have nothing to do with how much weight a truck can tow. You’re comparing apples to oranges.
Click to expand...
You're not the first one to say this. READ the article, they did it empty and with a 7,500 lb trailer. Very frusturating that some people are so qiuck to criticize with no actual reason to do so.
 
Jordan2929 said:
You're not the first one to say this. READ the article, they did it empty and with a 7,500 lb trailer. Very frusturating that some people are so qiuck to criticize with no actual reason to do so.
Click to expand...

Again, the article has nothing to do with max tow capacity.
 
Basic math, there is a reason the manufacturer states a 3:92 will tow 3000# more than a 3:21. Just go with that, no need to complicate it. Although not ‘legal’, someone should tow 20,000# with the same configured ‘19 1500 Ram trucks (or any brand for that matter) only difference being gear ratio, then you will see why. The more weight the more noticeable the difference. We have two farm semis which are as closely configured as you can get other than engine hp and gear ratio. One is 500hp with 3:55 ratio and the other 410hp with 4:33 ratio. The higher hp truck also has slightly higher engine torque. They both perform similarly when on the highway empty or even with half a load, but get them in a soft field fully loaded at 90,000# plus and the lower hp truck with the 4:33 will take off and go through the field and up the side ditch with less effort than the higher hp 3:55 ratio truck. A better test for the pickups would be to lock them, if you could, in 3rd gear and not allow them to shift either way, then put a heavy trailer behind them, once again same trucks only difference being gear ratio, and see what happens. Another thing to consider is the power/torque of the engine. As long as you are not maxing out the engine the gear ratio difference will not be that noticeable, but put enough weight behind it to max it out then you will definitely notice the gear ratio difference, and in that case, you will want the 3:92.
 
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Ok,

So I have purchased a camper and would like to share the numbers and get feedback.

Trailer
- GVWR 7,000

Truck
- GVWR from the sticker on my door - 7,100
- Payload capacity from sticker on my door - 1,667
- Curb weight - 5,433


So to calculate the payload on the truck:
- add my weight as the driver in excess of 150 lbs (first 150 lbs for 1 person is included)
- add other passengers weight
- add tonneau cover weight
- add running boards weight
- add mud flaps weight
- add bluox weight distributor hitch weight
- add tongue weight (15%) of trailer’s GVWR

Payload is 1,850, which exceeds my max of 1,667.

Calculate GVW of trailer (WITHOUT tongue weight)
7000 - 1,050 = 5,950 GVW of trailer

Calculate towing capacity:
Curb weight + payload = 7,263 GVW of truck
GCVW = 5,950 (GVW of trailer) + 7,263 (GVW of truck) = 13,213
GCVWR = 13,900

So as you can see, I’m good with everything except payload. When I look at the Ram website, it shows there’s a 3,000+ lb payload difference between a 3.21 and 3.92 axle ratio. To me, that means I could increase my payload by 3,000+ lbs simply by switching axle ratios.

My local dealer guessed it would be around $5k to do that, but I’ve called another dealer in my old city and they guessed (but are confirming) it would cost closer to $3k.

If I hear back for them that they’ll do it for around $3k, I think I’m going to do it. I’ll lose much more than that by trading in my 2 month old truck.

But I’m concerned because someone said that doing this won’t increase the axle ratio, but how could that be?

Also, do you agree with how I did my calculations? My camper dealer keeps telling me I don’t need to include the tongue weight when calculating the payload BECAUSE I’m using a weight distribution hitch.
 
c_l_phillips72 said:
Ok,

So I have purchased a camper and would like to share the numbers and get feedback.

Trailer
- GVWR 7,000

Truck
- GVWR from the sticker on my door - 7,100
- Payload capacity from sticker on my door - 1,667
- Curb weight - 5,433


So to calculate the payload on the truck:
- add my weight as the driver in excess of 150 lbs (first 150 lbs for 1 person is included)
- add other passengers weight
- add tonneau cover weight
- add running boards weight
- add mud flaps weight
- add bluox weight distributor hitch weight
- add tongue weight (15%) of trailer’s GVWR

Payload is 1,850, which exceeds my max of 1,667.

Calculate GVW of trailer (WITHOUT tongue weight)
7000 - 1,050 = 5,950 GVW of trailer

Calculate towing capacity:
Curb weight + payload = 7,263 GVW of truck
GCVW = 5,950 (GVW of trailer) + 7,263 (GVW of truck) = 13,213
GCVWR = 13,900

So as you can see, I’m good with everything except payload. When I look at the Ram website, it shows there’s a 3,000+ lb payload difference between a 3.21 and 3.92 axle ratio. To me, that means I could increase my payload by 3,000+ lbs simply by switching axle ratios.

My local dealer guessed it would be around $5k to do that, but I’ve called another dealer in my old city and they guessed (but are confirming) it would cost closer to $3k.

If I hear back for them that they’ll do it for around $3k, I think I’m going to do it. I’ll lose much more than that by trading in my 2 month old truck.

But I’m concerned because someone said that doing this won’t increase the axle ratio, but how could that be?

Also, do you agree with how I did my calculations? My camper dealer keeps telling me I don’t need to include the tongue weight when calculating the payload BECAUSE I’m using a weight distribution hitch.
Click to expand...
You're payload WILL NOT increase 3,000lbs by putting the 3.92 axles in the truck, although your towing capacity will go up considerably. You must've read the website wrong, there's no half-ton truck on the market with a payload even close to 4,600lbs. Personally if I were you I'd invest in some airbags (roughly $400) to go along with that weight distrubuting hitch, it will make the truck much more composed over those bigger bumps.
 
c_l_phillips72 said:
Ok,

So I have purchased a camper and would like to share the numbers and get feedback.

Trailer
- GVWR 7,000

Truck
- GVWR from the sticker on my door - 7,100
- Payload capacity from sticker on my door - 1,667
- Curb weight - 5,433


So to calculate the payload on the truck:
- add my weight as the driver in excess of 150 lbs (first 150 lbs for 1 person is included)
- add other passengers weight
- add tonneau cover weight
- add running boards weight
- add mud flaps weight
- add bluox weight distributor hitch weight
- add tongue weight (15%) of trailer’s GVWR

Payload is 1,850, which exceeds my max of 1,667.

Calculate GVW of trailer (WITHOUT tongue weight)
7000 - 1,050 = 5,950 GVW of trailer

Calculate towing capacity:
Curb weight + payload = 7,263 GVW of truck
GCVW = 5,950 (GVW of trailer) + 7,263 (GVW of truck) = 13,213
GCVWR = 13,900

So as you can see, I’m good with everything except payload. When I look at the Ram website, it shows there’s a 3,000+ lb payload difference between a 3.21 and 3.92 axle ratio. To me, that means I could increase my payload by 3,000+ lbs simply by switching axle ratios.

My local dealer guessed it would be around $5k to do that, but I’ve called another dealer in my old city and they guessed (but are confirming) it would cost closer to $3k.

If I hear back for them that they’ll do it for around $3k, I think I’m going to do it. I’ll lose much more than that by trading in my 2 month old truck.

But I’m concerned because someone said that doing this won’t increase the axle ratio, but how could that be?

Also, do you agree with how I did my calculations? My camper dealer keeps telling me I don’t need to include the tongue weight when calculating the payload BECAUSE I’m using a weight distribution hitch.
Click to expand...
Just curious. How sure are you of the !5% trailer tongue weight? If it was 10%, you would save 350lb payload weight and be under you payload rating.
 
Creep0321 said:
I do not believe the payload includes 150 lb driver. And 3.92 will increase towing capacity, NOT payload.
Click to expand...

I'm not sure about the payload number because I don't think it follows J2807, but the towing number assumes 150lb driver and passenger (300lbs total occupant weight), as well as towing equipment weight.
 
Last edited:
Your truck legally got its tow rating the day a VIN number was assigned to it. You can mod it but the rating for your truck will not legally change. If there is a incident and your insurance looks up the tow rating for your vehicle by its vin you will have a hard time explaining why it should be higher. I tow a 5200 Lbs dry / 6700 GVWR Travel Trainer with a 3.92 Laramie , I would not want to tow a larger TT long distances with it. For the TT you described I would want a HD Truck.
 
Try it with the 3.21 before spending any money on the 3.92 upgrade. It’s probably going to be OK.
 
Johnvan said:
Try it with the 3.21 before spending any money on the 3.92 upgrade. It’s probably going to be OK.
Click to expand...

I would pretty much go with 3.21 for my first truck, I guess once or twice per year is the maximum number I am renting a trailer and go out with my family


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