My Rav4 jumped out of 5th gear last week on the motorway last week and now wont stay in 5th at all, it's now started doing the same in 4th. Any ideas why and possible solutions please would be appreciated.
No but the effectiveness of a detent can diminish, if a synchro had craked and fallen apart I would expect more serious damage / noise as a result. They dont tend to fail without some serious abuse.
Eitherway a replacement box looks the easiest option
I suspect your gearbox oil level has fallen and the gears are gradually grinding themselves away. Can you hear a whining noise when diving?
Looks like a replacement gearbox is needed.
Sorry.
Synchro rings break up very frequently.
I was Ford's Transmission specialist for a while, and there were lots of problems with synchro assy's in certain boxes.
Detent balls and shafts just do not wear or wear out.