Not going into 4th gear sometimes.

[Chlorophil]

Hello all, So I've been having an intermittent issue with changing into 4th gear. Weather changing down from 5th to 4th or up from 3rd to 4th, it feels like it's gone in gear. I lift the clutch, and it's not in, accompanied by the sound of striking cogs. Re-clutch push it in, then it's fine.

My first thought would be linkage. I recently changed all the bushings, and it's had a fresh gearbox oil change and a 711 shifter, so I don't think any components are worn. Although I am wondering, as always, have I put it back together properly? 

It does this even when fully warmed up and only about 20% of the time. (sometimes this can happen when selecting second, but only when stone cold) It also never comes out of gear. When it's in it's in, it only has this issue selecting the gear.

For context, I have a 1986 van with 3H 5-speed.

Any thoughts? Does this sound like my linkage, or is it gearbox rebuild time?

[Aidan]

it may be worn synchro ring dues to overall wear and shaft displacement leading to the back of 3rd gear pushing 4th gear into it's ring and the synchrohub.

It could be one of the linear bearings that support the 4th 5th selector fork has broken, there will be evidence on the drain plug magnet, inch long piece of spring steel or 4mm ball bearings if this is the case.

But I'd hazard a guess, since it is worse when hot that the 4th5th synchro hub is cracked and broken and there is some camming of the parts occurring preventing the slider from moving freely over the hub. Total failure will be when you come up the motorway slip road and go to change down and the gearstick won't move and it remains stuck in 5th gear.

Unfortunately there aren't massive tell tall signs on the drain plug magnet other than usual wear signs and maybe a bit more head than usual, unless the keys are ejected by the synchroniser then they end up on the drain plug magnet.

[Chlorophil]

Thanks, Aidan. When I changed the oil, there was only a thin covering of metallic sludge on the magnet. There were no ball bearings or springs or anything in there.

It may be worth me refurbishing it at some point rather than waiting for critical failure, even if it's just for peace of mind.

[muttleypup]

For what it's worth, I'd check/adjust your linkage before anything else.  Given it's 2nd and 4th that are giving problems, and these are both selected by pushing the gear lever forwards, it may just be that you're not getting enough 'throw' to fully engage the gears.  There's a good video on Youtube re fitting the 711 shifter and making adjustments, search for James Akers, if you haven't already seen it.

[Aidan]

Did you resolve this ?