Crunching 4th gear

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21st February 2023, 09:36 AM
AzizY61

Crunching 4th gear

Hi guys,

My 4.8 2022 GU started to have a 4th gear crunch when shifting from 3rd to 4th. Vehicle odo is on 3000kms only!

I know this issue is popular with GU Patrols, but I can't see a 100% solution..

Does anyone know how to solve this problem?
26th February 2023, 01:33 PM
Canoath

Try changing old oil out with new Castrol VMX-M with Nulon additive. Also oil might be contaminated. If all else fails, then unfortunately it’s a rebuild job. Synchros are excessively worn.
26th February 2023, 02:07 PM
mudnut

Quote:

Originally Posted by AzizY61

Hi guys,

My 4.8 2022 GU started to have a 4th gear crunch when shifting from 3rd to 4th. Vehicle odo is on 3000kms only!

I know this issue is popular with GU Patrols, but I can't see a 100% solution..

Does anyone know how to solve this problem?

Nissan manual gearboxes require GL4 rated oil. GL5 is too sticky and will cause the syncros to stick cause crunching, especially when cold. It will damage the synchros over time.
27th February 2023, 02:53 PM
mudski

Quote:

Originally Posted by AzizY61

Hi guys,

My 4.8 2022 GU started to have a 4th gear crunch when shifting from 3rd to 4th. Vehicle odo is on 3000kms only!

I know this issue is popular with GU Patrols, but I can't see a 100% solution..

Does anyone know how to solve this problem?

If you find a solution I'd love to know. Mine is real bad, even with VMX-M and the Nulon smooth Shift additive it made no difference at all.
27th February 2023, 04:23 PM
mudnut

Quote:

Originally Posted by mudski

If you find a solution I'd love to know. Mine is real bad, even with VMX-M and the Nulon smooth Shift additive it made no difference at all.

Have you tried double clutching as on a none syncro box? From 3rd to 4th; Clutch in, gear to neutral, clutch out. Clutch in shift to 4th, clutch out. It might work and it gets easier with practice. I was doing it with my Old Trol while I was looking for a fix when it was crunching into second while cold.
27th February 2023, 08:45 PM
mudski

Quote:

Originally Posted by mudnut

Have you tried double clutching as on a none syncro box? From 3rd to 4th; Clutch in, gear to neutral, clutch out. Clutch in shift to 4th, clutch out. It might work and it gets easier with practice. I was doing it with my Old Trol while I was looking for a fix when it was crunching into second while cold.

Yeah but its a pain to do this all the time. I have to give the throttle a blip when going from 3rd to 2nd also. The box has done some 450+ thou, I'm just waiting for it to let go, Hopefully soon as I think the release bearing is shot and I don't want to do the clutch and not the gearbox. Well I don't want to do either really but...