If i get a 9.75 rear differential would it kill my truck if I get gears for the front and rear but the front are 8.8 and not 9.75 or would it not matter just as long as they are the same ratio(IE 4.10s or 4.56s)

 

As long as they are the same ratio, it will not hurt anything. The 4x4 F150 with a 5.4 comes standard with an 8.8 reverse cut front and a 9.75 rear.

 

I'm not sure what your asking but you need to get a reverse cut 8.8 for the front, and a 9.75 for the rear, both with the same ratio.

 

Ok I just thought that on the 5.4 the front was also a 9.75 inch ring gear but I guess not

 

The fronts don't need to be 9.75". Think about it. The only time the front is used is when the truck is in 4 wheel drive. Then, the torque is spread over both differentials. When in 2 wheel drive, the rear takes all of the torque and therefore needs to be 9.75".