Big Rock Big Rock lost power and grinding

[PatMarcus172]

On the advice of lots of forum members my lovely Big Rock got treated to some new Granite wheels today. So, I took it out for a quick lunchtime run. After a couple of rips it seemed to lose power and started making a horrible intermittent grinding noise that I hope Ive managed to capture in this video. I cheked the spur and pinion and both are fine, as is the drive shaft. The sound is definitely coming from the rear of the vehicle and its the rear wheels that have lost power and are spinning erratically compared to the front.
Is when things like this happen that I realise Im still a complete noob and neither know what to check or what its likely to be. https://drive.google.com/file/d/1jX1WQX8-WfeY_VXwGWJiyRbNeqCGrqHK/view?usp=sharing

Please help and save my Big Rock.

 

[Edough13]

It's probably your rear diff and input gear. Need to pull it apart and look but loss of power and clicking or grinding definitely is a chewed up diff and input pinion. Check jenny's rc for both, also it doesn't have to be for the Bigrock so check ALL 3s models for the parts

 

[BulletRCs_NZ]

I've done the Crown and input gear in my BR ... twice It was pretty easy to get out and change as a noob. Check out YouTube for a how to video.