Do you need to replace the stock HPI outdrive to use the T nut? I'm a bit stumped on this part. See as how the outdrive is molded to take the nut in it. Any help would be greatly appreciated
No...the only parts you need to replace are the diff screw, white t-nut, and spring. the AE TC3 diff rebuild set has everything you need.
Here is the diff mod
you can build it like the pic he attached....where you need to dremel the HPI outdrive.
or
just build it the normal way using the AE parts.
i have watched people use both ways with success.