I have proton waja 1.6A (auto)year may 2001, past three year with problem on gear box, while driving speed min.90 to 120 kmh, my gear will drop from 4 to 3 then the rpm will increase,already chg auto transmission oil but still some problen,

To clear the problem:- stop and off engine (before off engine gear position must be "P" ,
after 5 minite re-start engine gear move "R" and car must move bit to reverse than gear move to "D" then drive.

contineu having some problem for three years,
how to over come this problem, pls i need your assist

Regards/Thks
Ismail