How do you keep the GU's 5sp shifting smooth as butter?

I just got off of a 2000+ km journey with my newly purchased Patrol. It was shifting smooth as butter the first day I had it, and I was grinning ear to ear. But on the second day of driving, I noticed the shifting seemed noticeably "crankier". Instead of shifting smoothly between gears, it began to take some careful articulation, especially between 2nd and 3rd. Which is fine, but just not nearly as enjoyable.

How do you keep the GU's 5 speed transmission shifting smoothly? What kind of maintenance is required?

First, check that the clutch is disengaging properly. It wouldn't hurt to bleed the clutch fluid to get any air out of the system.

According to the workshop manual, page nine: the manual gearbox requires a GL4 rated oil 75w90. GL5 is too sticky and causes the syncromesh to grab and grind. I hope, for your sake, that the vendor didn't put additives in the box to quieten it down for the test drive. There are some situations where the oil/additives used are tougher than the brass components and will cause the metal to erode.

My suggestion would be to drain the box and fill it with the correct oil and see if it runs better.

Change the oil as stated would be a good start. I also add the Nulon G70 additive in mine, which has helped a lot, since the box is circa 450thou old. Only a matter of time for mine now though. What motor is in your Patrol too?

Thanks for the advice guys. I plan to have Nissan look into this when they service the ute (TD42) tomorrow.

Come back for a second opinion if they quote you anything stupid..

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Originally Posted by svocamper

Thanks for the advice guys. I plan to have Nissan look into this when they service the ute (TD42) tomorrow.

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Is it a stock TD? Mine runs with around 650nm, the first time I went away towing the camper I was pretty much on the go pedal in 5th and pushing it up hills etc etc and I found that when I came into a town and had to slow down I found it real difficult to change up gears. Turns out I had cooked the gear oil from too much load, eg flogging it up hills, a lot, with the camper in tow. After I changed the oil and changed my driving style all is good.

FWIW, don't bother taking it to Ni$$an for this. They'll just change the oil or tell you that a new gearbox is on the cards.

The service manager at Nissan tells me my current gear oil is in pristine shape.

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Originally Posted by mudnut

According to the workshop manual, page nine: the manual gearbox requires a GL4 rated oil 75w90. GL5 is too sticky and causes the syncromesh to grab and grind. I hope, for your sake, that the vendor didn't put additives in the box to quieten it down for the test drive. There are some situations where the oil/additives used are tougher than the brass components and will cause the metal to erode.

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I take it the current gear oil is likely GL-5 then. GL-4 was impossible to find locally; the best they had was Penrite Pro Gear Fully Synthetic 75W-85 rated "GL-4 plus". I'm having Nissan put that in for me, because it's the best I can manage in the short term.

Previously, the ute was owned by a retired pensioner in rural NSW, and I'm guessing the Nissan service center he took it to there didn't use GL-4 gear oil; the current one I'm at in a much bigger town didn't know what GL-4 even was or why it was applicable. I'm glad I brought in the Penrite, because they fully intended to use a mystery gear oil in its absence.

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Originally Posted by mudnut

My suggestion would be to drain the box and fill it with the correct oil and see if it runs better.

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This is a good suggestion. The service manager at Nissan here had me convinced not to change it out, but I went back and ordered them do it anyway just now.

On a completely different note, the Nissan service center I'm at right now truly had no idea what they were doing when it came to gear oil. In fact, they do not inspire confidence at all, except insofar as they are doing the least amount of work possible, and sign off on having performed work for record-keeping purposes.

The whole experience is making me second guess taking it to Nissan dealerships in the future.

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Originally Posted by mudski

Is it a stock TD?

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Its only notable modification is a 3" exhaust.

I hope the GL4 plus is not just a GL5. I had the same problem with shifting after my gearbox was changed out. I asked the mechanic which oil he used, and it turned out to be GL5.

I used Castrol VMX M GL4 and the gear change is silky smooth, even on cold days.

Your experience sounds pretty standard form for dealers. A reputable independent is nearly always better from my experience. At least they will do what you want even if it's not what the dealers hand book says.

Problems seem mostly gone now with the Penrite. It isn't entirely as buttery smooth as the first day I drove it, but I suppose road tripping 2000+ k's through rural NSW in rough conditions on GL-5 gear oil likely did some type of permanent damage to the synchros. It isn't perfect, but it's back to registering somewhere on the enjoyable scale at least.

As luck would have it, while the Nissan service center had my vehicle, I found and bought Penrite GL-4 75W-90, the perfect stuff. Ran back to Nissan but they told me they had already changed out the gear oil.

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Originally Posted by mudnut

I hope the GL4 plus is not just a GL5. I had the same problem with shifting after my gearbox was changed out. I asked the mechanic which oil he used, and it turned out to be GL5.

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I called up Penrite about their "GL-4 plus" rated product. The techie I spoke to over the phone explained it's essentially a GL-4 which substitutes out mineral oils for synthetics to improve anti-foaming and resistance to sheer.

So far so good, but then again I haven't driven it 2000+ k's yet. I have the proper GL-4 gear oil ready to go in case anything goes wrong with it.

This is interesting me. Is this gear oil choice only important for a particular model of gearbox?

How can I tell what model gearbox I have??

It will be on the vehicle ID plate. I think it is on the D/S firewall. Happy to be corrected if wrong.

I put GL5 in mine when I first got it (+ Nulon PTFE additive). The box was always stiff & clunky when cold,but ok once warmed up. I was later told about the problems GL5 causes in these gearboxes. I changed to the recommended GL4 & the cold change became as good as the previous warmed up change. Much better. I ran the GL5 for a couple of years. I don't believe any significant damage was done, the gearbox has been fine for several years since. Compared to most modern cars it's an old style gearbox anyway without the modern fine tolerances, just the nature of the beast.

Last time I changed the oil I used Penrite Pro 75W85 because a) it's GL4 & b) being full synthetic it flows easier than the equivalent mineral oil which makes putting it in so much easier. Very happy with it. It may be that the less viscous nature of the oil is the reason that I have found a couple of drips of oil (as other 4.2 owners have also reported) at the clutch/gearbox mating. I have kept an eye on this since & found it only occurs under hot & extended 4wd conditions. We are 'on the road' & I bought a couple of (expensive) litre bottles of the Penrite Pro to top up if needed.After driving from Katherine to Cairns via a fair bit of 4wd & slow corrugated routes I only noticed a couple more drips (literally that is all) the gearbox oil level has not noticeably dropped. Just a heads up so you don't need to panic if you find this happening.