Originally Posted by rc_square24

In my experience, leakage only happened at the outdrives and not between the case and pulley, whether its plastic or aluminum. Ive tried changing the amount of fluid I fill but they still leaked. Once I changed to xray 972050 orings it stopped the leak. They're a bit larger so has more drag but is leak free.

I think the diameter of the oring recess on the TRF419 diff cases are a bit too large for the Tamiya red orings. Even with the outdrive inserted, the outer edge of the oring just barely touches the wall of the recess. The depth of the recess is also greater than the thickness of the oring, so adding shims won't compress the oring to make a better seal.

IMO the aluminum diff case helps dissipate heat to keep the fluids more consistent and doesn't fix leakage if that's your problem. With the plastic diff cases I always sand the seating surface for the gasket to make sure its flat. The gasket is quite thick so maybe the sanding is not necessary, but I haven't had any leakage in between the case halves.

I ordered some Axon black and clear orings to test if they provide a good seal with less resistance than the xrays. Will report back the results.