I understand the big geat to little gear ratio concept. What I want is to understand how to interpert that into the numeric values I see posted for the truck. I am embarrassed to admit I can't appreciate some of the postings.

I have a 3.73 rear (from the sticker). I see postings for a 3.55 and I believe I seen other numbers like a 4.10. I believe the lower the number the a) better towing and b) worse mileage ... but my knowledge stops there.

Can someone make me a little smarter on this.

Thanks

 

Other way around! ... lower gear is higher number ... A low number or tall gear (3.55) is NOT always better mpg but could be used as a sort of a general rule. It depends on the driving conditions ... a lower gear or higher numerical such as 4.10 or 4.56 etc... can give city driving mpg gains ... and as a rule are better for towing usually.

 

The ratio refers to the number of driveline rotations per tire rotation. So a 4.10:1 ratio means that the driveline spins 4.1 revolutions per one tire revolution. This allows the engine to get greater mechanical advantage on the tires and allows it to run in within the RPM limits of the engine. The higher the number (sometimes refered to as shorter gears) the more revolutions of the driveline it takes to move the vehicle the same distance as a lower number ratio. This is better for towing heavy loads and starting off in general because it allows the engine to get into it's best torque producing range easier, but means that your engine will run at higher RPMs at a given speed, thus reducing overall gas milage. The opposette is true of lower ratios. You'll have a harder time taking off, especially under load, but at freeway speeds your engine is turning less RPMs so you get better milage.

HTH

 

Thanks pitrow. That makes perfect sense.

 

Quick question. Doesn't changing the gears in the back require you to change them in the front, for 4x4, also? Or is there a way of changin the gears in the transfer case or the transmission, so you don't have to touch the front and rear diff. How is that work?

 

Yes, you change both front and rear diffs. Usually trying to keep under 2% of each other ... such as a 4.10 and 4.11 could be used together and still be fine for highway use! Larger than 2% differences are sometimes used for off-road only applications.

 

So, if I bought my truck and it has the tow package, the 5.4L engine w/ 7050# gvwr tow package and the gears are 3.55, does that mean it is mis-matched? Should my gears be switched out to the larger #'s?