I went back and read some of your posts. By your dilema, I think I found 2 problems you addressed. The pinion gear and the rear diff.

You will have to replace the pinion gear. It is available in 15T or 17T (# of teeth). I strongly suggest also changing the spur gear at the same time. Make sure they are correctly spaced from one another or, one, the other, or both gears will be ruined quickly. You will ware out spur gears and how long they last will be determined by how the car is driven (assuming they were set correctly to begin with). Just the nature of the beast (so to say).

Regarding the diff issue: It is difficult to say what is going on without physically seeing the diff. This is an area where your dealer who sold you the Photon should be helping you with. If the diff was defective to begin with, we will send the dealer a replacement but we need to discuss that situation with the dealer your purchased it from.

I hope this info helps.