When you say crunching gears are you indicating that all gears crunch? Do they crunch if you double declutch? If not then it is your synchro rings that need replacing or the oil is too thick.Some people think that gear oil goes into an old gearbox ie EP90 ,engine oil is used and 30 years ago I use ATF oil with a moss box for hillclimbes with overdrive for quicker change and to today it is still working with no issues.
I suggest you drain the oil and replace with a modern 10/40 oil as an easy start to see if that helps
Regards Tony
I suggest you drain the oil and replace with a modern 10/40 oil as an easy start to see if that helps
Regards Tony