I got my truck about 3 weeks ago and never paid any attention to what my axle ratio was. I never even thought about it till I saw people on here talking about them.

I found that mine is 3.21. What are the advantages and/or disadvantages of this?

 

You should get better mileage, if you put larger tires or have the 20" wheels my dealer said it will affect performance with the smaller ratio.....mines coming with the larger and have only drove the larger ratio so i cannot compare.

 

Better mpg, worse for towing anything, IMO.

 

I have the 20" wheels on mine. I still have under 1000 miles on it so I assume my mpg will get better as it breaks in.

 

Highway mpg will be better, around town will be worse.

 

mine has the 321, I drove 2 weekends from dallas to corpus [806 r.t.]
the best I got going was 21.6 running 74 mph with a/c
I tow under 5,000 no problems?

 

Better highway mileage, worse city mileage, worse traction and worse acceleration.

 

Is there a code on the rear end or data plate that says what the rearend ratio is? Thanks

 

There is somewhat of a mis-conception about the comparison of 3.21 gears to other ratios for towing.

For trailer weights in the 5,000lb range and under:

Due to the shift schedules in the tranny; regardless of rear end ratios the trucks will seek 3rd gear when under increased load. The 3.21 and 3.55 will usually remain in third during steady state cruise while the 3.92 will only occasionally upshift to overdrive 1.

The point is that in third gear the engine RPM with the 3.21 ratio is in the ideal power range for cruise economy and light acceleration.

 

I found mine on the window sticker. I kept it and had to go back and look at it.