[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