An Engineer's Ultimate Guide To 3.21 VS 3.92 Axle Ratio

[silver billet]

So are there happy 3.21 owners out there? Seems most are 3.92 guys.

Mine will be 85-90% or more daily driver, so I thought I'd go that direction...in addition, I have the ORG and may consider the bigger Rebel Wheels on the Laramie...all of which could hurt my mpg. I don't drive like Mario Andretti (sp?), so figure I can keep the mileage reasonable - hoping 18+

Listen, I know you don't buy a truck for mileage, and I don't think the one should pick the Diesel solely to save dollars over time, because you probably wont...anyway...I've been picky on this, because it's my first half-ton.

Pretty sure the overwhelmingly vast majority of 1500's sold these days are 3.21. Rebels and special orders and a few dealers diddling make up the rest. So yes, 3.21 is the perfect gear ratio for most people. If you are that concerned about MPG, which you appear to be, the 3.21 is the obvious choice.

 

[BowDown]

Pretty sure the overwhelmingly vast majority of 1500's sold these days are 3.21. Rebels and special orders and a few dealers diddling make up the rest. So yes, 3.21 is the perfect gear ratio for most people. If you are that concerned about MPG, which you appear to be, the 3.21 is the obvious choice.

I'm happy with my choice, just drove about 40 highway miles for the 1st time since buying the truck in late July, Dallas to Fort Worth and got 24-25 mpg at 72mph.

 

[Grouper]

I'm ordering from the factory and I'm getting 3.21. I only pull my boat a few miles a couple of times a year for maintenance.

I just don't see a need for 3.92 and the extra RPM on the highway.

 

[bwsRam19]

Must be a regional thing, the lot I bought my truck from most were 3.92, its a no brainer for the extra 100 bucks. It will definitely hold 8th gear better on the highway.

 

[silver billet]

Must be a regional thing, the lot I bought my truck from most were 3.92, its a no brainer for the extra 100 bucks. It will definitely hold 8th gear better on the highway.

I guess you haven't read the entire thread, but "holding 8th gear" in 3.92 is identical to 3.21 holding 7th gear, they have the same final gear ratios. So you are distinctly at a disadvantage; if we want to hold same rpms as you guys, at the same speed, we gear limit to 7. And for the vast majority of freeway driving we still have an extra gear on top of you guys. You can't spin that as an advantage of the 3.92 once you understand how final gear ratios work (hint, completely ignore the numerical gear "7" or "8" and instead calculate the final gear ratio).

The "$100" should not be used to determine whether it's valuable. For a start, the 3.92 is probably physically bigger (so more material so more cost), it's an infrequently purchased option (so you pay more because there is less volume of scale); possibly even they charge just because they know if you need it, you'll pay for it anyway.

 

[bwsRam19]

I see your point, I don't have to mess with gear limiting, the truck performs how I want it to with the 3.92.

 

[silver billet]

I see your point, I don't have to mess with gear limiting, the truck performs how I want it to with the 3.92.

Right, but nobody with the 3.21 is messing with gear limiting either (unless we're pulling) for the most part. I regularly drive a 3 hour highway trip, including some steeper hills on the freeway. My truck spends 99% of that time in eight gear, saving me money over the 3.92. It downshifts maybe 7 times on that trip to go up the hills, 2 of those hills it downshifts to 6th or 5th (meaning, your truck would also have to downshift at least one gear).

The amount of time I spend worrying about my truck downshifting out of eight is right above the amount of time I spend worrying about the ants crossing the street

Finally; some of us mess with the gear limiting literally every time we put it in drive, to disable MDS. If we want to limit to 7, it's quicker and easier to limit to 7 than it is to 8.

I'm glad you're happy with the 3.92, I probably could be too, but the advantage of the 3.92 is just not there for the vast majority of those people who think they are benefiting from it. The 8/10 speeds have completely eliminated the need for lower gears like the 3.92 or 4.10's etc for most people at this point. If we had a 4 or 5 speed, the 3.92 would be much more important and beneficial.

 

[LakesAZ]

I have the 3.92 as that was what was in the truck when I bought it. So whatever the dealer loaded up on, and in my dealers case it was 3.92 rear ends, that is what you had to chose from. I like the low end getup and go that it has and like others have said, you can't buy a full size truck for its gas mileage. If you drive 10000 miles a year, 20 MPG would use 500 gallons, and 16 MPG would use 625 gallons. So they difference of 125 gallons at lets say $2 a gallon, is $250 a year. I'm OK with that but I know others will say they drive way more than that and that $250 could be $500 or more.

 

[bwsRam19]

I always buy the biggest engine and lowest gears offered in the truck im considering(if I can afford it). This method has never left me wanting more power.

 

[silver billet]

I always buy the biggest engine and lowest gears offered in the truck im considering(if I can afford it). This method has never left me wanting more power.

That's fine, the next guy says "I always buy a 2500 because it's far more truck (power + tough) and only a little more money". There are perfectly sound strategies for these purchase decisions. But unless you're constantly towing very heavy (which isn't my cup of tea in a 1500 anyway) or always punching it off the line, the 3.92 has no real world advantage.

 

[silver billet]

you can't buy a full size truck for its gas mileage

Why not? It's just as easy to say "you don't buy a full size truck to race from stoplight to stoplight". Keep in mind the vast majority of 1500's are limited by payload, so since you are limited to <= 8000 pounds towing anyway, and the 3.21 does the job perfectly well at that weight, my priority switches to saving gas.

 

[LakesAZ]

Why not? It's just as easy to say "you don't buy a full size truck to race from stoplight to stoplight". Keep in mind the vast majority of 1500's are limited by payload, so since you are limited to <= 8000 pounds towing anyway, and the 3.21 does the job perfectly well at that weight, my priority switches to saving gas.

I didn't say that the 3.92 was better than the 3.21, I was pointing out that I personally like the lower geared rear end. Everyone is looking for something different in a truck, but most of all they are bought for their hauling capacity. If you're looking to save gas money and don't intend to use it for towing or hauling stuff in the bed, then it would make more sense to buy a Prius.

 

[Rossum]

Everyone is looking for something different in a truck

This.

Wanna win stop-light races? 3.92
Tow big/heavy things regularly? 3.92
Mostly highway at 80 mph without a trailer? 3.21

 

[bwsRam19]

That's fine, the next guy says "I always buy a 2500 because it's far more truck (power + tough) and only a little more money". There are perfectly sound strategies for these purchase decisions. But unless you're constantly towing very heavy (which isn't my cup of tea in a 1500 anyway) or always punching it off the line, the 3.92 has no real world advantage.

It's funny you mention the 2500, because thats the truck I wanted, but couldn't swing it, so i settled for the next best thing. I tow a boat and trailer often, so I just prefer the most torque of the line.

 

[BowDown]

Must be a regional thing, the lot I bought my truck from most were 3.92, its a no brainer for the extra 100 bucks. It will definitely hold 8th gear better on the highway.

If that's a concern, read the earlier posts on thst subject in this thread

 

[BowDown]

This.

Wanna win stop-light races? 3.92
Tow big/heavy things regularly? 3.92
Mostly highway at 80 mph without a trailer? 3.21

I doubt you win many stop light races with the 3.92. I can flash the torque converter and mitigate any advantage the 3.92 has from a dead stop.

 

[bwsRam19]

If that's a concern, read the earlier posts on thst subject in this thread

Not a concern of mine, I have the 3.92

 

[bwsRam19]

I doubt you win many stop light races with the 3.92. I can flash the torque converter and mitigate any advantage the 3.92 has from a dead stop.

What if the 3.92 flashed their torque converter

 

[BowDown]

What if the 3.92 flashed their torque converter

If they new to do it, most dont

 

[z0n3]

In the process of ordering a 2021 Laramie. Currently I have a bighorn with 3.21 gears and heavy E tires. I put a lot of highway miles on the truck and the heaviest load it'll carry is a truck bed full of camping gear. I haven't noticed much of an issue with the 3.21 but there are times it seems to stick in a gear that is should move out of going up steady grades. Would there be any reason for me to switch to a 3.92 with the new truck?