Driving gear issue

[Bam@@]

I own Mercedes Benz C250 2013 model sports 1.8 liters engine turbo engine petrol with the chassis number (WDDGF4HB6DR295560) very recent i have issues with my car my car was not moving all the four wheel’s was stuck,i then call mechanic to check the fault he then told me the fault is the driving gear,He replace the driving gear but still the fault remains. I then take to Mercedes Benz dealership in Ghana,it have now com to my notice that the fault was not the back driving gear but the ABS sensor ,the dealership told me to go for old back driving gear,the one he replaced have different teeth.when i want to the mechanic workshop he can not find my old driving gear.
Kindly help me to no number of back driving gear teeth does my car have and the Axle ratio of my car is: 3.07