3.21 or 3.92

[bryan28]

How many mpg can i expect to lose if i opt for the 3.92 instead of 3.21? The truck will be a hemi 4x4 qc with the 8 speed. I drive probably 80% highway and 20% city. The most I'll be towing now is a 17' aluminum boat but may tow more later. The speed limits here are 70 so i usually set cruise at about 75-80mph. The terrain ranges from relatively flat to steep hills but mostly pretty flat that i travel on most.

 

[Csanders1992]

With how you plan on using it the 3.21s may be better. Although I'd still choose the 3.92, you'll be able to tow that trailer with ease and the hills you encounter will be easier. Plus it's more fun


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[CMil527]

For your needs 3.21 imo..

 

[Selcher]

The answer is always 3.92!

 

[blrmkrl83]

The towing limit for the 3.21 is about 8,000 lbs. vs. a little over 10,000 for the 3.92. That's probably not an issue for you. As far as the mpg goes you should be within one or two mpg of each other. You just need to decide what's more important to you, a little better acceleration or a little better mpg. If you're going to order one go with the 3.92, but other wise just find a truck you like and get it.

 

[dhay13]

i have a 2013 Ram 1500 QC 4x4 hemi with 3.55s and the 6 speed. my commute is about 70% highway and i consistently get about 17.5-18.0 MPG. i had a rental while my truck was getting repairs done and it was a 2014 Ram 4x4 QC hemi 4x4 with 3.92s and 8 speed. i got about 21.5 MPG in that with the same commute. some of that was likely the difference in transmissions but i could definitely feel a performance difference.

but as a compromise you could go with the 3.55s if they still offer them

 

[Burla]

Go test drive both. You usually gain MPG in the city with 3.92's and loose some on the freeway. 3.92's are the way to go usually IMO.

 

[14hemiexpress]

3.92 all the way. Better accleration better mpg in town better tow capacity. The only expensice is probably 1 mpg on the hwy the 3.21 and 3.92 are rated same mpg we all know that's not possible but there won't be much suffering.

 

[xrsman]

My answer is also always going to be 3.92. I drove both before ordering (even though I knew I wanted 3.92's) and there was a huge difference in power and I didn't notice a big difference in mpg. Maybe 1 mpg

 

[clh1220]

My answer is also always going to be 3.92. I drove both before ordering (even though I knew I wanted 3.92's) and there was a huge difference in power and I didn't notice a big difference in mpg. Maybe 1 mpg

Huge difference in power. Lmao

 

[xrsman]

Huge difference in power. Lmao

You disagree? At the same spot on the test drive I floored it from a dead stop. The 3.21 chirped the tires and took off. The 3.92 broke the tires loose and spun for 25 feet. So yes I'd say that's a huge difference in power to the ground.

 

[dhay13]

i agree the 3.92s feel completely different. night and day. no more power but the truck gets into its max torque range sooner. i know mine pulls unbelievably at around 2500 RPM but it takes a bit to get there where the 3.92 truck gets there very quick

 

[coleflo]

Your going to want 3.21's

No you're not.

 

[cgeorgemo]

With the 8 speed you'll be fine with the 3.21 if you only have a 6 speed then you might need the 3.92. The 8 speed's first 2 gears are lower then the 6 speed's 1st gear. The 6 speed with 3.21 will have more ratio than the 6 speed with 3.92 across the entire gear range until gear 8 and 6 which should be highway speed where the 3.21 will use less gas.
http://allparnews.com/index.php/2013/11/does-ram-need-lower-axle-ratios-23910

 

[cgeorgemo]

You disagree? At the same spot on the test drive I floored it from a dead stop. The 3.21 chirped the tires and took off. The 3.92 broke the tires loose and spun for 25 feet. So yes I'd say that's a huge difference in power to the ground.

I can get my Pentastar to break free and spin for 25 feet if I really want to. How does that help me pull a trailer?
The Hemi with the 8 speed has more than enough ratio to start a trailer like he is describing.

 

[rick-rock]

I would think that a 17 ft aluminum boat even with fish (the fish can't be that big) in the boat would tow just fine with 3.21 gears, 6 or 8 speed.

My budies Volkswagen could probally tow the boat, without the fish of course, or burning tires 25 feet.

 

[coleflo]

There has to be a reason why I've never seen a thread in a truck forum where someone was inquiring about swapping to a taller gear.

 

[xrsman]

I can get my Pentastar to break free and spin for 25 feet if I really want to. How does that help me pull a trailer?
The Hemi with the 8 speed has more than enough ratio to start a trailer like he is describing.

Maybe in the rain..the 3.21 on the exact same patch of freshly paved road would only chirp the tire. I didn't hold the break, the road was dry as a bone. The test drives were one after the other so the pavement wasn't any hotter. I simply took traction control off and put the petal to the floor. If the 3.21 couldn't break loose than I know in the same situation the penstar deffinitly couldn't.

My test is fact, not someone blowing smoke. I wanted to see the difference between the 2 from a take off and I did. I wouldn't bias one over the other in the test because if the 3.21 had surprised me and had similar take off I'd have got it.

 

[clh1220]

I drove both also and I didn't turn the traction control off on either. And there want that much difference. Go do your 1/4 Mike and 0 to 60 times and see.If we want to get into towing yours is treated more to you're but you still have the same truck, no better brakes suspension or frame. Your opinion and mine are not the same. The other guy on here there was a post about going to 3.21 from a 3.92. Oh **** I just realized where your at you guys don't do 1/4 miles. LOL

 

[Dubstep Shep]

I love the 3.92s in my truck. I could probably get a couple more mpgs with a lower ratio, but it still sits at like 2k rpm at 80mph. I get around 19mpg commuting to work so it's nice.