GQ gearbox crunching

[Drewboyaus]

Grinding gear into reverse could be signs of a clutch issue. Your slave cylinder is generally right next to your exhaust it could that.

Thanks man. What sort of thing should I be looking for?

[nissannewby]

See post #10.

You could try, when it's warm, just sit in gear with the clutch in on nice level ground. If after a bit with the clutch in and in gear it starts to creep forward then its most likely a master cylinder.

[my third 256]

syncro might be the issue also

[Drewboyaus]

syncro might be the issue also

I did wonder that but because it only happens when warm that perhaps it was something else.

[my third 256]

just speaking to my dad and he said sincro teds to fail more when box gets hot and oil is thinner
could try thicker oil and see what happens

[NP99]

How long since the last oil gear change?

[Parksy]

When shifting to reverse do you give the shafts in the gearbox a chance to slow down? I'm not sure if reverse has syncros, and mine crunches if I don't give it a chance to stop spinning. Avoid putting gl5 spec oils in the gearbox as this will eat away at your syncros. Gl4 only!
I'd be changing your fluids. Same with the transfer case. If you have manual locking front hubs, chuck proper gearbox oil in the transfer, if you have auto hubs, then ATF. But the gearbox oil seems to make things feel 'smoother'.

[Drewboyaus]

How long since the last oil gear change?

Doesn't get driven much, probably 8000k ago and 18 months......

[Drewboyaus]

When shifting to reverse do you give the shafts in the gearbox a chance to slow down? I'm not sure if reverse has syncros, and mine crunches if I don't give it a chance to stop spinning. Avoid putting gl5 spec oils in the gearbox as this will eat away at your syncros. Gl4 only!
I'd be changing your fluids. Same with the transfer case. If you have manual locking front hubs, chuck proper gearbox oil in the transfer, if you have auto hubs, then ATF. But the gearbox oil seems to make things feel 'smoother'.

Thanks Parksy.
I would have thought if it were a syncro issue I'd be getting grinding on both up and down shifts between 1 & 2.
It used to be the case where if I ran it through a 3-4 change and then into reverse I'd have less issues but it would still grind sometimes. That doesn't seem to work anymore.
What you describe is sort of what it sounds like but I do tend to let everything sit for a little while before selecting reverse.
I'm going to run Mattys test tomorrow if I can't get it into the shop before this weekends trip.
Something is nagging at me that he is right about the clutch master cylinder as I have this sense the pedal feel isn't quite right.

[Parksy]

One thing I've noticed with mine, and maybe it's all in my head, is the gearboxes ability to 'learn' how you shift. I don't really know how to explain it, but if I force the gearbox into gear quickly, the feel turns to sh1t, even if I want to shift normally. It takes about a week of normal slow shifting for the gears to select nicely again. Then all good again. Anyone else notice anything like this?
Btw, when did you last replace the nylon bushes on the end of the gearstick? If you have excessive movement here this can make shifting harder.