H55F and 3rd gear problem

[We Sing]

Hello experts,
I have an H55F gearbox, and it works fine! However, it keeps popping out of 3rd gear. If I hold the gear lever, it stays in gear. Even when the engine isn’t running, the lever just slips out of 3rd gear, as if a spring or something inside is loose.
Has anyone experienced this problem before? Thanks in advance!

 

[Eurasiaoverland]

Most likely the 3rd/4th gear shift sleeve and index teeth are worn.

Another possibility is that the detent mechanism on the shift fork shafts is faulty. How does it feel when you put the gearbox into 3rd? Is there any feeling of positive engagement?

Start by getting a FSM for the gearbox. Then remove the gearstick and check the retaining pins are not loose in the cover. Check also the rubber gearstick seat/base, as they commonly wear.

Next, remove the gearbox cover and inspect the index teeth on the input shaft/3rd gear.

You can strip down the shift fork/shaft assembly in the cover with nothing more than a hammer, some pin punches and a screwdriver.

To go deeper and change gears is a lot more involved.

 

[We Sing]

Most likely the 3rd/4th gear shift sleeve and index teeth are worn.

Another possibility is that the detent mechanism on the shift fork shafts is faulty. How does it feel when you put the gearbox into 3rd? Is there any feeling of positive engagement?

Start by getting a FSM for the gearbox. Then remove the gearstick and check the retaining pins are not loose in the cover. Check also the rubber gearstick seat/base, as they commonly wear.

Next, remove the gearbox cover and inspect the index teeth on the input shaft/3rd gear.

You can strip down the shift fork/shaft assembly in the cover with nothing more than a hammer, some pin punches and a screwdriver.

To go deeper and change gears is a lot more involved.

Thanks for your answer. When I shift into 3rd gear, it feels normal. You hear the shift noises, but the gear lever just falls out due to gravity. This happens even when the engine is off. I have the FSM and a complete gearbox rebuild kit. I want to rule things out first. I’m going back to investigate today! Thanks so far!

 

[We Sing]

Most likely the 3rd/4th gear shift sleeve and index teeth are worn.

Another possibility is that the detent mechanism on the shift fork shafts is faulty. How does it feel when you put the gearbox into 3rd? Is there any feeling of positive engagement?

Start by getting a FSM for the gearbox. Then remove the gearstick and check the retaining pins are not loose in the cover. Check also the rubber gearstick seat/base, as they commonly wear.

Next, remove the gearbox cover and inspect the index teeth on the input shaft/3rd gear.

You can strip down the shift fork/shaft assembly in the cover with nothing more than a hammer, some pin punches and a screwdriver.

To go deeper and change gears is a lot more involved.

I took a closer look. You don’t hear a click in 3rd and 4th gear. In 3rd, the gearstick just falls down when the engine is off, and when you shift to 4th, there’s no proper click either... no positive engagement I think.
Sounds like a detent mechanism issue... The gearbox probably needs to come out from under the car.