What difference does topping up gear box oil make, tooki my furby in garage and apart from setting timing again they have topped up gear box oil, was told it will make major difference but cant understand why. Not got furby back yet but his words on phone were vast improvement, How come???

Well if the gear box oil is low you would potentially get a poor gear change.

Topping it up would make the gearbox smoother, not to mention is last longer

Over more years than I care to remember I’ve always changed the gearbox oil – and it’s been interesting to see what’s stuck to the magnetic drain plug. The worst offender was a Citroen – about 15 years ago - that had collected so much swarf at 5000 miles that as a precaution I changed it every 5,000 for the next 30,000, by which time it was almost clear. The box lasted undisturbed until the car was sold with 175,000 miles on the clock - whilst similar models were known to fail at around the 100,000-mile mark. Today it’s rare to see any accumulation of metal on a drain plug, just a discoloration of the oil. However, I believe that the boxes of some makes are now sealed. On a related point, how about sealed-for-life engines with automatic oil top-up? Impossible? Well, one of my ex-pupils works as a development engineer for a well-known European engine-development company and engine test rigs run on behalf of one large manufacturer (she won’t say which, of course), have already racked up the equivalent of 200,000 miles + plus with no problems.

Only car I've ever had where you could even check the gearbox oil is the Impreza.

I've gathered (internet, mags etc) that the major cause of gearbox failure is lack of lubrication/oil. So it's definitely something worth keeping ones eye on.