Mt gear crunch, lots of trial.

[kivig]

Hi,
2008 1.3, 140kkm/100kmi. Symptoms I'm sure many have heard here about, but "the hope dies last" :)
When the car is moving all gears (5th to a lesser degree) show some random resistance and notchiness engaging, and the 2nd randomly grinds teeth.
Much worse when cold.

With no effect:
Clutch was replaced.
Clutch was bled multiple times to whats in total probably a big beer mug of fluid (no signs of any leakage on clutch cylinders).
Gear oil was replaced with Castrol Syntrans FE75, Update: now Toyota LV 75W.
The gearbox was disassembled and inspected, concluding - it's almost like new, except noticeable wear on second gear axial teeth.
2nd 4th gear synchros and a couple of bearings were replaced "just in case".

Before disassembling the gearbox I've read here about probable factory undersized gear selector shaft, but inspecting it there was no free play in it anywhere and no signs of wear on the sides of gear shift heads (notches by which shafts with forks are moved) that probably would be logical to expect in case of misaligned engagement in-between them.
Edit: flywheel runout seems ok (about 0.01mm/.5thou or less), input shaft not rusty/dirty.

Any speculations? Thanks.

[komichal]

The only thing I am missing in your list is original Toyota gearbox oil. Try that as well. :)

[2bz]

The lube used is GL4 75W. That's essentially the Toyota spec. Should be ok

[tmontague]

The lube used is GL4 75W. That's essentially the Toyota spec. Should be ok

Is it a straight 75w oil though? If so then it is too thin at operating temps

[kivig]

Is it a straight 75w oil though? If so then it is too thin at operating temps

The idea was, as suggested manyplace on this forum with mostly positive feedback for situations like this, to use the thinnest oil allowable, to increase ability of synchros to pierce it.
And even with that - as described - it's not even close to enough when below 0C - then I have to carefully push it for a solid second or more to avoid gear grind or just floor it and skip to 3rd and then 5th.
It's better at moment as it is warmer (maybe due to new synchro too to some limited extent), but the realization that it still skips a tooth or two, slowly filing the gear away every time I flick the knob a bit faster in traffic is not something I'm used to tolerating when it comes to machinery.

Starting to lean towards finding another gearbox and replacing most of it.

[komichal]

The lube used is GL4 75W. That's essentially the Toyota spec. Should be ok
You can find not just a few examples here in the forum where users used original Toyota oil and it solved their problem - despite the fact that the non-original oils they used before did meet Toyota specifications fully and their brand was sound.

[kivig]

You can find not just a few examples here in the forum where users used original Toyota oil and it solved their problem - despite the fact that the non-original oils they used before did meet Toyota specifications fully and their brand was sound.

It's just that the mechanism of how the oil could fix things (by not being too thick) seems to be already there. But it is cheaper than a gearbox, so might be worth a try. Will check whether I can find original.
Edit: also it is likely that the oil I've already replaced was from factory...

[kivig]

Yesterday I replaced oil with Toyota LV 75W. There might be some minor effect due to it's viscosity being a few percent lower (or it just got warmer outside), but still - second gear synchro isn't capable of grabbing the shaft fast enough, skipping teeth in about 25-30% of gear changes and the rest of gears are struggling.

Probably will have to look for a used gearbox for parts still. Any idea what should be replaced?

Then again - is there any way to positively test whether the clutch is not dragging?
Bell housing has a convenient ventilation hole (rectangle rubber water protector that can be taken out) to stick a camera in. Unfortunately the spring plates and release bearing obstruct the view of shaft rotation.