Question about Rear Axle Ratios
 

I'm thinking of buying a new truck and i have the option of a 3.55 Axle Ratio, Limited Slip Rear vs. a 3.73 Axle Ratio, Limited Slip Rear


Basically this means nothing to me, so any info would help. At the moment all that I will be pulling is an ATV (which will be in the bed). Which would provide more "umph"/power? or speed?.

Thanks for all your help!!!

The larger the rear end ratio, the more the eninge has to spin to turn the wheels the same speed.

A higher ratio will get you marginally faster 1/4 mile time, and the ability to pull a heavier load more easily.

BUT

A higher rear end gear will get you less gas mileage on the highway.

Honestly, there isn't much difference between a 3.55 and a 3.73.

Now if you were comparing a 2.93 and a 4.11, that would be a dramatic difference.

You may also have to consider the kind of transmission that is in the truck, 3.73's work really well with overdrives.

But honestly, the 3.55 would fare you better gas mileage in the long run.

;)

-SF

The 3.55's will net you marginally better highway mileage, but 3.73's will likely net you better around town mileage. Also note that the "higher" gear ratio saltfish is referring to is a numerically higher gear ratio. When tossing the terms for rear gears around, "low gears" will refer to a higher number numerically. i.e 4:11=low, 3.08=high.

The term limited slip is often interchanged with the term positraction. Basically, there are clutches in the rearend that will distribute power to both wheels, rather than a single rear wheel. I would personally go with the 3.73's, but then again, if I tow anything its usually the wagon or the firebird.

Thanks :)

Tire size makes a difference too.
The larger the tires the more gear you need.
If this is a stock truck and you only plan to tow the A.T.V. I'd go with the 3.55 for better gas mileage.
Gas prices are going nutso.

On another note, if you have 4WD you should consider your ratio a little differently. I had a Blazer with a B&M shift kit and 4.11:1 gears. It was really fun with my 400 small block, but would spin the wheels too much in some off-road applications. (i.e. I pretty much buried it in the outer banks of N.C. when I hit the gas a little too hard). Live and learn for me, I guess. Oh yeah, it also got about ten gas-guzzling MPG on the highway. ;)

I would say go with the 3.73's, there is no need for a higher gears than that, such as the 3.55's

Saltfish has summed it up nicely. Your talking about less than 5% difference in final drive ratio. But if you do a lot of highway driving the difference (at ~20mpg) is in theory about 1mpg better for the 3.73s. If your getting about 10mpg it's only 0.5mpg

3.73's will do just about anything a person needs to do, unless you like to hook onto obnoxiously heavy things and move them.

I tend to do that a lot, so every truck I ever owned had 4.11's in them. I accept my fate of abysmal mileage. :)

Good question...and good answers.

Now I understand why my 2.20 final ratio is a "high speed cruisier" (i.e., a "grand tourer") as opposed to a drag racer.