Axle Ratio

[TrojanDan]

Sorry if I'm putting starting this thread in the wrong place, but there's no offroad topic or axle topic, so I figure this is the best place for it. Anyway, I'm just startin to learn about offroad stuff, and one of the major parts is axle ratios. I'm familiar with the 3.73:1, 3.92:1, 4.10:1, and 4.56:1 ratios, but on the offroad package on the website, the titans axle ratio is listed as 3.357:1 ratio. They also say that its "similar to a 4.10:1 ratio on a 4speed automatic". Can someone explain what that means? How can it be similar, when it seems so different? Why is there a difference, aren't all axle ratios the same? Does it have to do with the type of axles that they use? Thanks for your help. I'm a new member, becuase I'm heavily considering the Titan, and I'd just like more info before layin down so much cash. Thanks bros!!!

[keane]

Originally Posted by TrojanDan

Sorry if I'm putting starting this thread in the wrong place, but there's no offroad topic or axle topic, so I figure this is the best place for it. Anyway, I'm just startin to learn about offroad stuff, and one of the major parts is axle ratios. I'm familiar with the 3.73:1, 3.92:1, 4.10:1, and 4.56:1 ratios, but on the offroad package on the website, the titans axle ratio is listed as 3.357:1 ratio. They also say that its "similar to a 4.10:1 ratio on a 4speed automatic". Can someone explain what that means? How can it be similar, when it seems so different? Why is there a difference, aren't all axle ratios the same? Does it have to do with the type of axles that they use? Thanks for your help. I'm a new member, becuase I'm heavily considering the Titan, and I'd just like more info before layin down so much cash. Thanks bros!!!

Simple answer is the axle ratios are exactly what they say they are. The difference is in the Tranny gear ratios. Because the Titan uses different tranny ratios their 3.357 ratio for their rearend actually gives the same RPM at any given speed as a 4:10 ratio on the domestics. Hence The Titan's equivelant rear ration of 3.357:1 is the same as competitors 4.10:1

[TrojanDan]

Originally Posted by keane

Simple answer is the axle ratios are exactly what they say they are. The difference is in the Tranny gear ratios. Because the Titan uses different tranny ratios their 3.357 ratio for their rearend actually gives the same RPM at any given speed as a 4:10 ratio on the domestics. Hence The Titan's equivelant rear ration of 3.357:1 is the same as competitors 4.10:1

thanks bro, you are a true stud with a huge unit!

[PHOEBISIS]

The axle ratio is the ratio of the numbers of turn the drive shaft turns,to get one turn of the wheels.For example,if there were 10 teeth on the drive shaft,and 40 teeth on the axle gear,then it would be a 4 to 1 or 4.00 axle.
To know The actual total ration of engine turns to rear wheel turns you have to know the gearbox ratios also. 5TH gear in the Titan is .83 to one.It means for .83 turns of the engine,you get one turn of the drive shaft and less than 1/3 turn of the rear wheels with our 2.94 or 3.36 rear end(3.36 teeth on the wheels shaft,to one tooth on the drive shaft-you can't have 3.36 teeth of course-it is probably more like 47/14 or so).
So in 5th gear the engine turns .83 turns-the axle turns 1 turn,and the rear wheels turn 1/3.36 turns or .297 turns.
To figure the speed at a given RPM in a given gear you need to know the tire height-you can measure,or calculate that.It is about 31.4" or 2.61 feet-the circumference is 2.61X3.14=8.21 feet is how far you travel with one turn of the rear wheels.
60 MPH is 1 mile a minute = 60miles/60minutes.To figure your RPMS at 60mph in 5th gear you find out how many wheel turns it takes to go a mile
5280/8.21= wheel turns 643.11 turns per mile.
Multiply 634X 2.94= 1890 drive shaft turns in 5th.Multiply 1890X.83=1569 rpms 5th gear at 60 mph.
Sorry I switched to the 2.94 instead of the 3.36,but I realized that the 17" tire on the XE is 31.4" and only comes with the 2.94 ratio.The 17" tire on the SE,LE Offroad is 32.6" same as the 18" on the SE,LE on Offroad.
You would want a low gear offroad (there is another gear in there to drop the gearing even more-more engine rpms,fewer turns of the drive shaft))because you want to be able to crawl along at idle in a lot of tight places,not go 10-15 mph like most cars will at idle.It also helps in going downhill-the engine turns more and provides engine braking.
For MPG you would want the tallest(smallest rear end number) gear the motor can turn without lugging-(feeling like it is straining,and slowing down).For acceleration you want a low(big number) rear end.
I think Nissan means that the 4th gear in our trucks with the 3.36 is like a 4 speed with the a 4.10 if their 4th gear is an OD gear like .83.His final gearing in 4th would be .83x4.1=3.4 a lot like our 3.36 in 4th-4th gear is 1/1 one turn engine,one turn drive shaft.


The 18" wheel(actually 32.6" tall) 2.94-gives about 1530 RPMs at 60 mph.
Well,I almost certainly screwed this up,good luck,Charlie

[TrojanDan]

Thanks for the great info bro, it helps to have it all explained. I'm lookin to lift the Titan (when i get one) and put 35 or 37" tall tires on there. I want a lower axle ratio (higher numerically) so the engine doesn't have to work so hard to turn those big tires.

[bestatchess]

Originally Posted by TrojanDan

Sorry if I'm putting starting this thread in the wrong place, but there's no offroad topic or axle topic, so I figure this is the best place for it. Anyway, I'm just startin to learn about offroad stuff, and one of the major parts is axle ratios. I'm familiar with the 3.73:1, 3.92:1, 4.10:1, and 4.56:1 ratios, but on the offroad package on the website, the titans axle ratio is listed as 3.357:1 ratio. They also say that its "similar to a 4.10:1 ratio on a 4speed automatic". Can someone explain what that means? How can it be similar, when it seems so different? Why is there a difference, aren't all axle ratios the same? Does it have to do with the type of axles that they use? Thanks for your help. I'm a new member, becuase I'm heavily considering the Titan, and I'd just like more info before layin down so much cash. Thanks bros!!!

You multiply 1st gear ratio (transmission) x transfer case low range x axle ratio to get what is known as "crawl ratio". The bigger the number, the lower the gearing. On top of that, you have to consider the tire & wheel size, as the tire outer diameter also factors into the effective gear ratio. Crawl ratio is important for off-road use, as there are some trails that you want to go very slowly on, yet still have good torque. You can't get the complete picture by just looking at the rear axle ratio, you have to consider the entire drive train. If you look up (or calculate) the crawl ratios of a few different vehicles and then go to the dealer for a test drive and put it in low gear, low range, you can get a good appreciation for the significance of the gear ratio numbers. For example, go check out a Jeep Wrangler Rubicon - manual transmission, 4.10 axles, which has a crawl ratio of something like 65:1 and compare that with a Titan, which has a crawl ratio of about 33 (off-road or Big Tow). Anyway, stick both of them in 1st gear, low range, 4WD, and note the speed difference idling down a steep hill. Then all these numbers will make sense to you.