Hi, I have a UK model Hilux 2010 1KD with A750F transmission. I've noticed sometimes it does not shift into 5 gear and gets stuck in 4th. Restarting engine usually fixes it and it happens randomly. there are no codes or anything that might point to an abnormality.
Can anyone guide from where to start troubleshooting. I was thinking to change transmission oil but WS oil is expensive and I'm not sure if changing it would benefit or bring more harm. I dont know of its service history. mileage is around 125k miles.