As title says won't change up just changed the gearbox filter and fluid and it drove perfect thought it was cured went out last night to a pals came to go home and it wouldn't change out of 1st again 40 mile to get home after 2 miles it changed up perfect and worked as it should all the way home put it in P on my drive and it rolled back so it's not locking up in park. Any ideas appreciated. Atb Ed

not changing up is a common govenor issue on a worn box after oil change, though if you change filter you have to ensure you use 2 o rings, park not working could be incorrect cable adjustment often were cable is secured to mount or broken park wheel

Didn't happen to me but a friend had a similar issue a while back. Turned out the gear selector cable was loose. When lever shows D it's actually in 1 only. Try the cable first. Took a mate 20 mins getting dirty but fixed for free