The teeth are worn out at an angle. This pushes them apart when under a load. Probably starts out just kicking out at high speeds then gradually kicks out all the time, then the teeth totally wear out and it doesn't work at all. I'm sure you have high miles on the car and since you are in 5th gear most of the time, that is why that gear wears out before the others.
-In other words, your transmission is shot.
My 1995 Metro jumps out of fifth gear when the gear is worn out. I had the transmission rebuilt, and fifth gear replaced, at 150k miles and fifth gear replaced again at 220k miles. The transmission shop that did the second repair told me that fifth gear is located outside the main part of the housing and is not lubricated by direct contact with the transmission oil. Instead the oil is pumped by the action of the shaft into a channel and spout system that pours oil on the gear. Part of this system is plastic and prone to damage. Even when working perfectly, the system tends to under lubricate fifth gear, in their mechanic's opinion. On the plus side, it is not necessary to remove the transmission to get at fifth gear, they can just remove a housing to inspect and replace it. On the down side, it still costs hundreds of dollars if it has to be replaced. I had a general mechanic perform the rebuild and the transmission specialist speculated that he probably was not familiar with all the components of the lubrication system for fifth gear and didn't replace it properly. They could not even find one piece that was essential when they did the second repair. I recommend taking it to a transmission specialist that has worked on metros.
Sounds like you've got worn out syncros on the 5th gear. ~ Tim ~
Jumping out of gear in a manual transmission is usually a sign of a worn detent in the internal shift linkage under the shift cover. This usually requires a rebuild of the transmission.
If your combo van is jumping out of gear and won't engage fifth gear, it could be due to a worn or damaged gear selector mechanism, a faulty clutch, or issues within the transmission itself, such as worn synchronizers or gears. Additionally, low transmission fluid levels or contamination can lead to shifting problems. It's advisable to have a professional mechanic inspect the transmission to diagnose and fix the issue properly.
Sounds more like a transmission mount. When you drive it if it doesnt jump when it shifts gears then more than likely its a mount.
Worn synchros
Mail Call - 2002 Paratrooper Jump Gear Weapons Communications Medical Gear 4-11 was released on: USA: 11 April 2004
Mail Call - 2002 Paratrooper Jump Gear Weapons Communications Medical Gear 4-11 is rated/received certificates of: USA:TV-PG
dun no, sorry dude
really its on jump duck
When the transmissions in these tractors get worn, they will jump out of gear. Usually first and third gear will do this first, and if the transmission gets really worn other gears may jump out.
Jump Tomorrow - 2001 is rated/received certificates of: Australia:PG UK:PG USA:PG