I am looking at new Chevy Trailblazer brochures, and it says axle ratio is 3.42, and axle ratio 3.73 or 4.10 are options that I can get for additional %50 (either ratio). What is axle ratio and what are pro(s) and con(s)? Thanks.
What do you plan on doing with it? Do you plan to tow? Is it going to be a "soccer mom" transport? Can you drive one with each ratio? (It becomes pretty obvious if you can drive 'em back to back the difference between the rear gearing.)
an attempt to explain what the end result would be... The "default" ratio of 3.42 is 1st - 4th gears just like normal. The 3.73 gears would be like having a gear lower than 1st and no more 4th gear. The 4.10 gears would be even more extreme.
You could also think of a ten speed bike:
3.42 rear gears = speeds 5,6,7,8 off the ten speed. 3.73 gears = speeds 4,5,6,7 4.10 gears = 3,4,5,6***4.10 gears are "lower" even though the number is higher*** (it's a 4.10:1 ratio - like 41 teeth on one gear, 10 on the other.)
What are the differences? You'll be able to accelerate stronger with the lower gears. Your engine will rev higher on the highway with the lower gears. (increased fuel consumption) If you're towing or driving in hilly terrain the lower gears may prove to be better. If you plan on jacking it up and putting 36" tires on it, the lower gears will be a good idea.
*** all of the above is "assuming all things are equal" - if you get the 4.10 gears and the big tires, the highway rpms could very well be the same as the 3.42 gears and small tires. ***Ray
To try to be a little more concise in Ray's explanation, the axle ratio is the ratio between the number of revolutions the driveshaft makes in relationship to revolutions the tires make. If you have the 3.42 ratio, your driveshaft will turn 3.42 times to make the tire turn once.
The pros for the lower numerical ratio is that you'll get better gas mileage, your engine won't be turning as fast to keep your car at the same speed. That's pretty much the major advantage. Disadvantage is that you will not accelerate as fast and you won't be able to tow as heavy loads as if you had a higher ratio.
The advantages of the higher numerical ratio (4.10's) is that you'll get a higher towing capacity and faster acceleration. The down side is that your gas mileage will suffer.
The reason I said numerical ratio is because a higher numerical ratio is different from a taller gearing. A taller gearing means a smaller numerical ratio. 3.42's are a taller gear and a lower numerical ratio while 4.10's are a shorter gear and a numerically higher ratio.
There are other advantages and disadvantages but most of them are insignificant in relationship to gas mileage and acceleration when talking about axle ratios.
The ratios are based on simple division. 4.10 gears are 41 teeth on the ring gear and 10 teeth on the pinion. The pinion gear is driven by the driveshaft and the ring gear is attached to the differential which drives your axles and in turn turn your tires. 3.73's have 41 and 11 respectively and 3.42's have 41 and 12. Divide the first number by the second and you have your gear ratio.
If you're a visual learner, go here:
-Bruce
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