I have recently observed positive air pressure built inside corolla 13 gear box with 13000 km on clock. Initially I thought the gears to be hard, so decided to open screw to check the level of gear oil as I suspected that low from factory. Oil level was ok but I witnessed the air coming out with pressure. problem with hard gears was already solved. I repeated this process after a weak and this time, still there was some pressure but lesser then before. But since then gears are smooth as cream.
I thought, maybe it?s was a problem with my vehicle but later test drove a friends corolla 13 with only 22000 km on clock, I realized that his gears were harder than it was on mine initially. I performed the same exercise on his vehicle and witnessed air coming out with pressure. problem with hard gears on his corolla was also solved.
I think, it?s a generic fault on this model as reference is that gears should remain as smooth as once it came from factory throughout the vehicles life span. (Provided you change the gear oil on time)
This is public awareness message as first I think it should not be happening on such a popular vehicles. secondly I have realized that many don?t even notice that their gear shifts are harder and it does makes you feel uncomfortable.
Rest of the user can authenticate and verify if I am right or wrong and reasons for this.