GQ gearbox crunching

[Drewboyaus]

Looking for your thoughts peeps on what might be going on with my gearbox.
It's been going on about 18 months but think it's got a bit worse lately.
When the 'box is cold all is as it should be. It's when the temperature rises after driving for a while that things aren't right.
What happens:
1. Reverse won't engage without grinding.
2. Downshifts from 3-2 (not so much) and 2-1 become really stiff and hard to engage but no grinding.
All up shifts are fine while this is going on.
As it's got harder to slot reverse (it goes in but grinds), it's concerning me with some high country trips coming up that it will create a dangerous situation out there.
Clutch also seems to be operating properly.
Does anyone have any thoughts or encountered it before?

[MudRunnerTD]

It's a Nissan

[Drewboyaus]

Fo real.....,?

[nissannewby]

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

[MudRunnerTD]

Sorry Drew, all I got mate. Constructive though I thought!

Newby is about, he might have some options for you.

When was the last time you changed gearbox oil? Maybe time for some fresh oil and like a slick50 additive or something. Sorry all I got mate without telling you to rip er out.

[MudRunnerTD]

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

^^^^^^^see told ya^^^^^^^

;)

[Drewboyaus]

Sorry Drew, all I got mate. Constructive though I thought!

Newby is about, he might have some options for you.

When was the last time you changed gearbox oil? Maybe time for some fresh oil and like a slick50 additive or something. Sorry all I got mate without telling you to rip er out.

No worries mate. Just wasn't sure if it was a legit criticism of Nissan boxes.

[MudRunnerTD]

No worries mate. Just wasn't sure if it was a legit criticism of Nissan boxes.

From my experience with a 1992 and a 2005 Nissan gear box, Yes they can be a little notchy mate. So probably a bit of both bud.

[Drewboyaus]

Hmmm. Might have to see if I can get it out to 4x4 Obsession during the week.

What has me bemused is that it only seems to happen once everything gets warm....

[nissannewby]

Hmmm. Might have to see if I can get it out to 4x4 Obsession during the week.

What has me bemused is that it only seems to happen once everything gets warm....

Yeah once everything has heated up fluid maybe able to bypass a seal in your master or slave cylinder.

[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.

[Drewboyaus]

So I can't get it into the workshop until next week. Making me second guess the trip this weekend.........

[Drewboyaus]

Ok, so with some help from MudRunner and the awesome bloke Brett at 4x4 Obsession in Melton had a look at it today for 10 minutes and it turned out to be some clutch adjustment that was required. Matty, you were on the money in the right area.
Unfortunately I am at the end of my adjustment now and it is nearly time for a new clutch.
But I am on my way again......