First post so hello and thanks for letting me in. Currently have an Octavia 2 1.9 diesel - my first Skoda. Having driven old Land Rovers & Bedford vans for many years it is by far the most bafflingly modern vehicle I have ever had!

 

Anyway, been having the familiar 'gears getting stiff when hot' syndrome. I have reset the cables which has improved things (at least I havent got stuck in a supermarket car park with no reverse since!) but its still not right. Next step is to replace gearbox oil - 140k so cant go wrong changing it!. I have checked this forum so I have an idea what to do. I assume I just fill it via the reverse switch hole - switch is presumably the only thing on the box with wires just behind the starter (looking from front) ? Just open drain plug and put in same amount that comes out. But what oil to use? Seems to be various recommendations here. Thanks for any advice.

How is the gear stick when hot side to side floppy or very stiff. Vs when cold. 
I had this on my Octy 2 removing cables from gearbox proved it was gearbox. I removed and cleaned selector arm pin. Gear change improved. I am sure I wrote a post on it. 

Tends to be stiff all round when hot, fine when cold. I tool one of the cables off, the rubber wasnt great but the collar was fine. I was intending to replace the end rubbers at the same time as changing the gearbox oil.

I'm sure you can shim the box to remove play on that model, also has a few drain holes and a set procedure for draining and filling. Can only be don't by draining and refilling the box as the oil level is above the filler hole. You refill from reverse switch.