Can anyone explains what rears are

It refers to the ratio of how many times the drive shaft will turn in order to turn the wheel once.

So it is 3.21 revolutions and 3.58 revolutions to turn the wheel once.

The lower the number is a ratio that is meant for higher speeds and better fuel efficiency, while a higher number allows for greater pulling power especially when getting started or going up hills

Everything is a trade off as there isn't one right axel ratio it all depends on what your driving environment is.

 

Oooh the places this thread could go

 

This is the rear axle or axles gear ratio. the higher the number the lower the ratio.. Its like 1st gear in your car transmission is lower [for starting out] but 4 th gear or overdrive is higher, for highway driving. As for the 3.21 or 3.58 it means the pinion gear that is connected to the driveshaft turns 3 times. The ring gear which is attached to the axle will turn a quarter or half turn. So the truck will have a faster top end speed with the 3.21 and the 3.58 will have a lower top speed but will have a lower take off speed, but will get a heavier load moving. Hope this helps. Stubby

 

Too much Max.....forget it. If you were at a 2.32 Walmart rear end and wanted 4.10 for dirt work, then maybe. k?

 

i like big buts....lol jk

short and simple of it is lower the gear (numerically higher) the truck will get rolling easier and pull hills better the higher the gear (numerically lower) the more sluggish the truck will feel although slight improvement on mpg on flat land. the best gear is typically a gear that puts you at peek tq at your normal cruising speed in top gear.

given the choice between the two ratio's posted i would choose the 3.58's any day.

another way some guys go about it is with a 13-18 speed high gears and run in 12th or 17th and pop it into top gears when on the flat lands. a lot of it is personal preference as well as what type of work and what area you are running in.