rear diff help plz
 

hey everyone ive got a 1/5th fs racingpetrol maurader that had a knackered rear diff so i got the new gears and cant get them to fit in the case lol im registered blind but see a little bit so good instructions would be good how to get them both to fit in, if you wondering i loved rc cars before i lost my sight then i did but refuse to stop with rc cars lol,
sorry if in wrong part and happy christmas and new year to you all