Hey whatsup guys. I wanted to know if it was possible to check a differential to see if it has a particular set of gears. I was going to change the gears on my car, but i found a mustang 5.0 being parted out, so ima get his 8.8 differential that already comes with a tlok( i think ) and just change those gears, but he had told me that they already come with 4.10's. I always tend to be on the safe side, so i would like to know forsure before i install them and find out their just stock gears. so If any of you know how i could be able to check, and if i could use my same axles with that 8.8 diff, or if i would need his axles.

 

It's actually pretty easy. Jack the car up, and count how many revolutions of the drive shaft are requried to turn the rear wheels one time. A 4.10 will require 4.1 driveshaft rotations to turn the wheel 1 time. If the axle is already out it's even easier.

A chalk mark on the tire and shaft help for reference. And yes it really is that easy.

 

Oh alright, cool man thanks, i will do, but now im stumped, i thought it was backwards, like the drive shaft turns once and moves the wheel 4.10 times, becuase they way you explained it, the lower the gears, the less the driveshaft needs to turn in order to move the wheel one time. you get me? so im lost now..

 

think about it this way, if the wheels turned 4.10 times per driveshaft rotation, an engine turning 3000 rpms in high gear (1:1 transmission output ) the tires would be turning 12300 rpms.

So since a 205/65r15 tire has a circumference of around 78 inches that is 6.5ft per rotation or 80,000 ft per minute that comes out to about 900 mph.

Conversely, with the drive sahft turning 4.1 times to turn the wheels once, the wheels are turning 730 rpm, or 4800 ft per min or 54 mph.

There was some rounding in this so these are not exact.

Also remember the drive shaft turns the pinion gear. The pinion gear turns the ring gear. Pinions have fewer teeth (in this case the ring has 4.1 times the teeth of the pinion)

 

Ohhh i get you. yeah, the other way would make my car pretty fast huh? lol thanks for the explanation man