Ive built so many diff with my husband on our multiple emaxxes (3)and all our friends slash 4x4 three total slashes., I love traxxas but there bearing tolerances, durability are horrible the worst i have ever used in a rtr. If i were you i would pick up a set of avid bearings. $20 shipped as a starting point , also Shims are your best friends,did you shim by chance? it almost sounds like its shimmed to tight in the first video. I have a winning 11 month old on my lap so i might not of heard right. Ive had the same sound when i shimmed the diff to tight and also when a small part of the crown gear greaks and wedges off in the gear also when the screws in the diff cups back out. I know you come asking for advise and not ways to spend money so sorry if thats how i come off. Also emaxx,erevo plastic diff cup case with the i bar will make it just about bullet proof. The aluminum diff cup is popular i have not needed one in my emaxx diffs with huge proline rock rage tires, but some people do.
Its not just a hobby for the boyz anymore & traxxas is still changing the game