Summary

Because a plastic gears in original project can not withstand a lot of load from the 540 motor, I have made some modification for a chassis and insert the Feiyue differential. And now the buggy is standing full power but a suspension arms needed to reprint from SBS instead ABS.
See my video with test run:

https://www.youtube.com/watch?v=2s7V9TxbHRU

This modification still uses the original plastic gearbox, which I made from PETG, and its connect to diff by Feiyue driveshaft. Also I used Feiyue driveshafts for a rear wheels and edited a rear hub model, because the wheel axle too short for two bearings.

Part list:

• WLtoys 540 motor

• Servo MG996R

• Feiyue differential

• Feiyue wheel driveshafts

• Feiyue central driveshaft

• Some M2, M2.5 screws, 2mm and 5 mm steel rods (I use nails).

The gearbox assembled as original project, but I was edited the big gear and now the central shaft fastens with a transverse 2 mm rod. The central shaft made from 5 mm rod and have two 2mm holes, one to Feiyue central driveshaft on end.

Rear part of chassis edited for the Feiyue differential. At first the differential must be screwed to the bottom plate, and both next screwed to another rear part. Also some juts on the differential body must be cutted. All gap between the diff body and the printed rear part was filled with a hot glue to improve strength.

Rear hub now contains only one 625 bearing and it fixes by spacer part which glued from the inner side with super glue.

Wheel adapter screwed to rim with M2 screws and nuts, also need some thin steel rod (nail) for rear axle.

Original 3d printed stereeng arms I replaced to carbon arms with joints from a Kossel 3d printer and it works much better,