I know most manufacturers of modernish cars put long life oil into gearboxes and almost seal them for life....

My car is renowned for bearing failiure in the gearbox... so I have a theory that changing the gearbox oil regularly might prolong the life of the box...

What are peoples thoughts on this... do we think fresh oil every 20,000 miles will help that much?

The trouble might well be that because the gearboxes are designed to be sealed for life they're not designed to be re-filled so you might find you'll have to take the box out to refill

Its fairly easy to drain/refill.... have done it in the past..

Just curious to know if actually doing this is worth the effort and considerable cost

I believe that 30-35k miles is what i always do in my normal tintop.

Which reminds me, in my next service i have to change it.

Surly it can only do good things.
After 20k change the oil as you want to and just inspect it.

See if the viscosity and colour differ much from the original and also look for little bits of metalic flec in the oil. This shows that there is wear in the gearbox somewhere.

Depending on the results of your investigateion you can decide if it was worth while or maybe just to change the service milage.

HTH.

hmm.... might be worth the effort....

Just need to work out what oil I actually need to buy... too much choice and conflicting information

If it does not have a filter or a magnetic plug then you may well just stir up the crud unless you give the box a proper clear out