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I though it would be worth to write a little bit more about GR6, it's weaknesses and possible fixes and upgrades, which are available through us.
There are some misconceptions and myths about this box so this might help clarify things.


One of the first issues that is often brought up is the heat management. In this box this is quite important for two reasons:

1. the oil itself has to be a compromise between hydraulic actuation oil for the gearbox selection system and traditional transmission lubricant managing friction between gears. This makes it quite low viscosity fluid because of the actuation system and operable only in quite narrow temp range.

2. the gearbox electronics themselves are floating in gearbox oil, which acts as a isolator and is not harmful to circuitry - but only up to certain temperature level - that is why the car will switch into limp mode to prevent electronics damage.

The gearbox runs TM oil-to- ENG coolant heat exchanger as standard and this acts both as a means to warm the oil quickly when the car is cold as well as cooler when the TM oil is too hot. It's adequate in typical conditions but not perfect for usual reasons (manufacturing costs, simplicity etc).

There are two kinds of add on's that can reduce the problem that may be expected in sporty driving - external oil coolers and radiators for the box itself.

We offer both solutions, manufactured by our technical partner in NZ - Doson Motorsport.

First being billet alloy sump with cooling ribs


Second being external oil cooler introduced into underfloor airflow:



The sump may be good addition to a typical service/upgrade done to the box on mechanical side, as the sump has to be removed almost every time with servicing anyway. And the cooler is advisable for those who plan on very fast driving, especially on the track.



Anther important factor for the possible unreliability of the GR6 is that system of locking shafts and cogs in place. They employ as standard circlips for both the shafts, FWD gears, and even the clutch pack casing. It is not a surprise the the vibration and extreme forced that these circlips are subjected to can sometimes make them slip off. This ends in catastrophic failures destroying lots of other gearbox parts by means of metal debris being thrown around.

Parts very developed to substitute standard circlip lock with something that is properly bolted. Those come for standard shafts, new upgraded ones employ typical system with self locking nuts instead of standard.

The locks would like like this:







These are CNC machined from billet steel and you can see how they Lock as compared to standard item on the third photo.


The third typical cause of problems is the dual clutch pack. The design is really trick, but unfortunately one can see some serious cost cutting in manufacturing. If you look at this photo

On the right hand side there is one of the standard clutch baskets. It's a steel sheet pressing with small billet part laser-welded to it. The pressing can be of various quality and generally tend to vary in clearances, fitting, depth of the groves for the previously mentioned circlips holding them together. This can lead to many problems with judder, slipping, excessive wear and loosing drive because of the circlip falling out. The solution we would offer is on the left - billet machined basked, secured by circlips that are bolted to it for additional security.


Finally the most commonly known problem is that sometimes 1st gear won't survive massive torque of the GT-R engine during launches and similar. This is true although it is much less common from what I know then people usually think. We offer PPG upgrade which has proved according to many people in the industry to be reliable (regardless of what some people say of PPG's reputation). The machining quality is very high and the gear itself is much wider and bigger then OEM:



It may be a good idea to change it if someone plans to race the car in 1st gear in any way.





This is by no means something to exhaust the topic of the GR6, or upgrades or maintenance, it's just short information on typical issues, I hope it may provoke discussion, questions etc.
 

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very interesing

could you give rough prices to install some of these?
 

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Discussion Starter · #3 ·
It's very dependant on the condition of the gearbox and if it is and upgrade or a fix of something that already has broken. We had a car in that had FWD gear fall off the shaft into the front drive clutch pack casing, than bits of that gone into oil pump drive and all over the valve block and gearbox internals - massive damage made by a small part.

Small upgrade that is recommended - so removal of the sump and front casing, mechanical lockers instead of circlips and inspection of the clutch + installation of the magnet kit to remove metal debris form the oil is same of cost as you would pay for larger periodical maintenance in your NHPC, larger things go into very high amounts of money up to the something like 1/3-1/2 of the price of the new box. But new box still has all these manufacturing faults.


I currently have two estimates in front of me - one is for upgrade for track day car with standard engine + remap and exhaust, the other is for top spec box avaliable now (some bigger upgrades are in development).

The bigger amount is for 15000GBP, the smaller one is for 6445GBP. The 6,5k one is something I would relly reccomend if someone wants trouble free running of the car.


Other thing is that every car will require clutch change at some point, as they only have about 1mm of the friction material in each multiplate clutch-pack. And Nissan does not offer such replacement - we do.
 
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