Just finishing up a makeover on my son's E10's front axle. I was extremely surprised when I opened up the axle to find STEEL GEARS! I guess that's part of the reason he hadn't broken anything in/on his axles in over 2 years of near daily use, but I had no idea that was even a thing. I did manage to break a rear dog bone last week, so I ordered some $12 SCX10 cv shafts for the front and put the good front dog bones in the rear. A buddy gave my son his stock AR60 diff cup/iron cross locker, and some well used overdrive gears which all dropped right in with no shimming.
We also bought some 1/8" npt x 1 1/2" brass pipe nipples that fit in the housing almost perfectly, I just put a dab of e6000 to keep them from rattling. These are only there for weight (about 1 1/2oz) and do not extend far enough out to require any housing modification (c-hubs do not screw in to them.) If you wanted to get the most out of it, you could certainly start with longer nipples, drill & tap them for the c-hub screws, and shave the rib near the outer ends of the inside of the plastic housings, and have the poor man's equivalent of beef tubes... but for the cost/effort involved, I'm happy with the outcome.
His front now steers about 40° with no binding, limited by the knuckles hitting the front of the c-hub (stops are shaved, c-hub screws are counter sunk) but the cheap cv's go just a hair over 45° on their own. I also added an 1/8" spacer to the tie rod to get the inside tire turning sharper at full lock, which makes the tires a little toe out when going straight. A worthwhile trade off if you ask me.
We also recently made a few more changes to his electronics. We switched from full time 4ws to 4 mode 4ws using my old RS10 radio. Installed a Holmes Hobbies Trailmaster Sport 27t 550, and Castle BEC set to 6.5v to feed both of his mg958 servos.
With all the previous chassis changes (full length chassis with incorporated shock towers and lots of adjustability, smooth skid with triangulated lower links, homemade forward battery & electronics mount, 100mm shocks) his 1.9 tire'd E10 can really give the more mainstream cars a run for their money! My 7 year old likes to remind the naysayers that it's "just a Redcat" when he crawls right past them.... but it's just barely a Redcat anymore.