Jumping out of 3rd gear

[timbigden@icloud.com]

I have a 4 speed box with synchromesh on 3rd and top.
Occasionally the car jumps out of 3rd gear on overrun. I have seen a post or thread on this problem but can’t find it now!
Engine and gearbox are coming out soon, so wanted an idea of what needs attention?

TIA

[AustinWood]

There is a small ball bearing and spring for each selector rod that locates the rod in posoition. The spring is probably either weak or broken on the 3rd/top rod.

[Graham Barker]

Also check that the edges of the hole where the ball sits are not burred preventing free movement of the ball.