hi there i was wanting some advice on wat to do to stop my box crunching in 3rd and 5th, its only happens when ive been driving for a while, there was one time when i was giving the car a hard time for a good 3 hour and it started crunching in 3rd 5th every change and a wee bit in 4th. ive been told that i need good gearbox oil, i think its just stock in it wat would you suggest??