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

Mirowpl

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This thread started on January 15, 2020. Here we are over 4 yrs later still discussing 3.92 Vs 3.21 To me it’s very simple, if you tow a lot or what you tow is near the max for your truck can tow, then get the 3.92 gears. Otherwise the 3.21 work fine for the rest. This assumes only that you use the truck for real truck thing like hauling lumber or firewood or towing a boat/trailer. It does not take into consideration those who want to drag race at a stoplight or brag about all the goodies they added like the jeep people do. I drive a truck, it’s dirty all the time, and it is stock from the factory with 3.21 gears. I can tow my 21 ft boat,tow a 16 ft trailer and otherwise do what I need. I am happy
 

Rick3478

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This thread started on January 15, 2020. Here we are over 4 yrs later still discussing 3.92 Vs 3.21 To me it’s very simple, if you tow a lot or what you tow is near the max for your truck can tow, then get the 3.92 gears. Otherwise the 3.21 work fine for the rest. This assumes only that you use the truck for real truck thing like hauling lumber or firewood or towing a boat/trailer. It does not take into consideration those who want to drag race at a stoplight or brag about all the goodies they added like the jeep people do. I drive a truck, it’s dirty all the time, and it is stock from the factory with 3.21 gears. I can tow my 21 ft boat,tow a 16 ft trailer and otherwise do what I need. I am happy
Yeah, we digested all that in the first couple pages of the thread. We jus' playin' with it now. 😁
 

HSKR R/T

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Maybe, maybe not but what we do have is known HP/TQ, known weight and known gear ratios. The 3.92 truck should be both faster and quicker however its neither. The only time the 3.92 truck outperforms the heavier 3.21 truck is when loaded with 7500 Lbs. IMO, 3.92s are more gear than this truck needs and while they may "feel" better, they don't seem to actually perform better.

Until someone lines up two identical trucks sans the gears, this is what we have, everything else is just 3.92 jibber jabber

View attachment 176789
As you continue to jibber jabber trying to rationalize why two different trucks had different outcomes, and we should use tht as an example of why gear ratio was the only difference that matters
 

Bt10

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I've posted before, but as a reminder, we have both of the trucks listed in the drag race. My ORG has the Falkens, not the Duratracs. WITH STOCK TRANSMISSION TUNING, the 3.21 wins because it spends less time in reduced power torque management.

Counts Custom had a customer request the 5 speed auto, even with some late model hellcat motor, because he wanted to feel the torque longer between shifts. Too few of gears that allow the engine to drop out of it's powerband would also be counterproductive.
 

BowDown

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:LOL:

People are still peddling this?

The hp to weight thing is not 1 for 1. As it goes up the ratio goes down. The Ram has 100 hp less than a 4 door sedan with the same motor? Not likely.

Precisely, too many small differences between these two trucks. I’d love to see two identical trucks just for S’s and G’s.

As you continue to jibber jabber trying to rationalize why two different trucks had different outcomes, and we should use tht as an example of why gear ratio was the only difference that matters


Me: Showing you that water is wet
You: Stomping your feet, no its not, not its not.
 

BowDown

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I've posted before, but as a reminder, we have both of the trucks listed in the drag race. My ORG has the Falkens, not the Duratracs. WITH STOCK TRANSMISSION TUNING, the 3.21 wins because it spends less time in reduced power torque management.

Counts Custom had a customer request the 5 speed auto, even with some late model hellcat motor, because he wanted to feel the torque longer between shifts. Too few of gears that allow the engine to drop out of it's powerband would also be counterproductive.

Even in the face of proof, deny deny deny
 

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