Which Oil for my Manual Gearbox GQ

[mudnut]

So which brand did you use? As I have to double clutch into 2nd when the box is cold.

[nissannewby]

Hi-tech oils mate.

[mudnut]

I will ring the mech who did the change out, and see if he can tell me if he used gl-5. Thanks, Matt.

[nissannewby]

I will ring the mech who did the change out, and see if he can tell me if he used gl-5. Thanks, Matt.

Does it specify gl-4 for the rb30 box?

[mudnut]

Sorry for the delayed answer. The original owners manual specifies GL 4 one of the after market manuals reckons 4 or 5

[Alitis007]

Gl-5 is ok but the synchros in the Nissan box behind the 4.2 ( petrol and diesel) and the 3.0 diesel (all the same box) much prefer the gl-4 oil. I cannot comment on the box behind the rb30 mate but if the manual specifies gl-4 then this is what I would be using. I changed from a gl-5 to a gl-4 oil in my patrol and noticed the difference nearly straight away. My box had dramas down shifting to 4th from 5th and also 4th to 3rd once the gl-4 oil went in this has probably gotten 50% better. I don't think it will get better as the damage may have already been done prior to me purchasing the vehicle but alls I changed was the oil.

The difference between gl4 and gl5 is the synthetic additives in the oil, gl5 has more that gl4 so unless the viscosity is different how does less friction modifiers make your synchro's mesh easier ??? I'm pretty sure the gu gear box uses a straight 75w oil but can't remember if the gq uses a 80w90 or a 75w aswell

[mudnut]

When I did the gearbox oil change last year, before it died, I researched the issue. Apparently early on, when gl5 oils were first released, the gl5 additives that coat and attach to the synchros are stronger than the brass. When they are worn off, they take a small proportion of the brass with them. I was assured by Nulon that the problem had been rectified with more modern oils. But now I'm not so sure, so I will have to shell out for the gl4.

[nissannewby]

The difference between gl4 and gl5 is the synthetic additives in the oil, gl5 has more that gl4 so unless the viscosity is different how does less friction modifiers make your synchro's mesh easier ??? I'm pretty sure the gu gear box uses a straight 75w oil but can't remember if the gq uses a 80w90 or a 75w aswell

It's well documented across these sorts of forums. It just seems the materials used in the boxes I mentioned earlier prefer the gl4 and I was just passing on my experience with the two different oils. Some additives in the gl-5 can attack yellow metals (brass,copper etc) which could possibly shorten the life. If it specifies gl-4 oil then why use something else? . Sometimes you can have to much of a good thing and it may be the case with the newer gl-5 classification.

[Alitis007]

When I did the gearbox oil change last year, before it died, I researched the issue. Apparently early on, when gl5 oils were first released, the gl5 additives that coat and attach to the synchros are stronger than the brass. When they are worn off, they take a small proportion of the brass with them. I was assured by Nulon that the problem had been rectified with more modern oils. But now I'm not so sure, so I will have to shell out for the gl4.

It's well documented across these sorts of forums. It just seems the materials used in the boxes I mentioned earlier prefer the gl4 and I was just passing on my experience with the two different oils. Some additives in the gl-5 can attack yellow metals (brass,copper etc) which could possibly shorten the life. If it specifies gl-4 oil then why use something else? . Sometimes you can have to much of a good thing and it may be the case with the newer gl-5 classification.

Cheers guys! I know with new diesel motors the friction modifiers affect the particulate filter but didn't realize it had that sort of effect on the synchro's aswell

[MudRunnerTD]

I have copied this out of BA's Members ride thread because it is useful and will get lost there.

Thanks Matt, George and Craig. Good info.