B. Sc. E. E. from a well known university.
I dont like to share too many details. I work in technology, know how tech companies abuse our information, and know that our digital footprints and fingerprints are already far too extensive!
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An Engineer's Ultimate Guide To 3.21 VS 3.92 Axle Ratio
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I dont like to share too many details. I work in technology, know how tech companies abuse our information, and know that our digital footprints and fingerprints are already far too extensive!
Lol. Ditto (of course). And completely understand. Not that your truck details aren't basically a fingerprint or anything...
Agreed. Like I said, our digital footprints and fingerprints are already far too extensive!Lol. Ditto (of course). And completely understand. Not that your truck details aren't basically a fingerprint or anything...
What kind of scenario, assuming you are operating within limits of load and towing, would 3.92 be able to do something 3.21 wouldn't?
I know 3.92 can get you "started" more easily, but once you are going, it's somewhat of a wash (in general terms and without getting into the weeds).
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I know 3.92 can get you "started" more easily, but once you are going, it's somewhat of a wash (in general terms and without getting into the weeds).
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Scram1500
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Crawl at a snails pace in 4Lo
Also turn larger diameter tires without affecting performance as much. Just going up one aspect ratio from the OEM 32" to a 33" tire changes the 3.92 to a 3.79. The 3.21 becomes 3.11
For a slightly more extreme example, 35" tires with 3.21 has an effective ratio of 2.95
Thank you.
I wonder about going to a 33. 4th gen rams had 33 as stock and also had 3.21s. Why would it be different?
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Scram1500
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Fuel consumption and chasing EPA regulations. 33" are heavier than 32" therefore less fuel efficient
Buz
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People always say it’s a wash after 2nd gear but I always compare the two ratios to the front sprocket on a 10 speed bike. The 3.92 is the smaller front sprocket and the 3.21 is the larger one.
Even if you match the ratios to get identical RPM’s (or pedal speed on the bike) it always felt easier to accelerate when on the smaller front sprocket. Maybe it’s just in my head.
Even if you match the ratios to get identical RPM’s (or pedal speed on the bike) it always felt easier to accelerate when on the smaller front sprocket. Maybe it’s just in my head.
I'm starting to think it's minimal at 33 for the user, but when combined across all the vehicles on the road, it looks better for the epa or whatever. The 4 gens had 33s and 3.21, the gmc and chevy trucks have some options that pair 33s and 3.23 rears.
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Great discussion. Follow up question. If the engine is the 6.0 liter diesel, and you are towing a 4500lb trailer, is the 3.92 necessary? Yes, it does increase the towing capacity, but the 3.21 capacity is well above planned towing. Thanks for your replies and input.
Morenar
Well-Known Member
Other than the window sticker and build sheet. Is there a way to look under the truck and know for sure which ratio you have? Maybe some stamping. I have heard on other brand forums where people thought they got the right axle ratio and ended up not being what was on the sticker.
Another way to know I would suspect is to compare your RPMs at a certain speed. Like post your RPMs at 70 MPH and I am sure people will let you know very quickly.
Can we assume the 3.92 is around 200 rpm ahead of the 3.21 from a start to whatever you reach? If so, it should be fairly easy to figure out with a dyno graph....
where can I or we find that graph? I don't know jack about this stuff (obviosuly)...
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I suspect someone on here has dynoed their truck and posted it...maybe in the performance/engine mod section?
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