GU Auto front hubs

The auto hubs don't lock in reverse so you would be able to reverse in 4L

Leroy

As long as you're going in a reasonably straight line and not for any great distances, you can quite comfortably have it in 4WD on a hard surface. The advantage of the auto hubs come into play if you happen to be in a situation where you didn't expect to need 4WD and can then do so easily, rather than having to get out once to lock the hub and then to unlock (sometimes saving embarassment).

The auto locks do lock in reverse Leroy.

Apparently they unlock that's why it's recomended to manually lock the hubs.

There may or may not be a momentary unlock, but they do indeed lock when reversing. Otherwise you would only have a 2WD if you had to reverse in adverse conditions (had to do that many times). If what you say is the case, then the Nissans could go just about anywhere in only 2WD. You have to take it out of 4WD and reverse to completely unlock them for normal driving.

NissanofOld is quite right.....the hubs only disengage in reverse if you've knocked the stubby lever fully forward.
As for being able to reverse in a straight line whilst pushing a trailer up a steep incline, you ain't seen me drive yet!!!! LOLOL
The other factor I STILL can't get a definitive answer on is this business of "Shift On The Fly" that Nissan say the auto-hubbed Patrol is capable of. As far as I'm concerned, you can only shift from H2 to H4 (while the vehicle is moving) if the hubs have been fully locked in (ie: using the wheel brace on the standard hubs). I tentatively tried to do it when i first got the GU, without locking the hubs manually. Even at ridiculously low speed (say 20kph), I could not encourage the transfer case into 4H from 2H.....it would start to grate. I gave up and still believe this can only be achieved when vehicle is at a standstill. With the hubs locked (either with the original hubs or my aftermarket ones) there is no worries, even at 80kph, because the from prop shaft is already spinning at the same speed as the rear shaft. So when you pull the lever back, the transfer case is not trying to get the front shaft to go from DEAD STILL to SAME SPEED AS REAR SHAFT in a split second.

Out of interest were they the Nissan auto hubs or those of another make. If Nissan, did he lock them in with the nut when off-roading or left them in auto. Locking them manually makes a big difference as to how long they last. How you grease them also make a big difference. Too much grease and the hubs won't work properly and then you will also have problems.

Also be aware with AVM, unless they have redesigned their hubs, that the earlier ones internally consisted of lots of small springs. Water would eventually get in and stuff the springs and you were then up for new hubs (rebuildable the AVM hubs might be, but no where could I find spares when mine went). The Nissan design is very simple in design, with solid components and with little to go wrong.

Nissanofold,

AVM have changed their design and they are just as simple as the Nissan ones. also for the price you could carry another set as a spare.
After seeing the damage caused to the bearings and stub axle by a broken auto hub on someone by the side of the road I replaced mine with AVMs the next day.
What happens is this:
On cold days when the transfer case is cold, as you drive the drag from the thicker cold oil causes the front hubs to lock, but since the vehicle is at speed the spring brakes and then it does a lot of damage, so it is not when you are using them that the damage accurs it is while they are on free...
You will find a warning on this in the manual, it says if driving in the snow in 2wd you hear a noise, engage the hubs (or somehting to that effect).
That is the reason why Nissan specify the trasnfer case oil to be ATF... while the early GQs were gear oil, so changing the transfer case oil to gear oil = damaged auto hubs.
I also love to backup my trailer into the steep concrete driveway in 2wd low...

Auto freewheeling hubs of the type that you can't manually lock up have been prone to failure (again, was it a Nissan with broken hubs you saw?)- I remember this from the early Pajeros and Jackaroos. The Nissan ones, which you can manually lock, effectively become full manual hubs (if so locked) and won't disengage or work any differently to a fully manual hub.

The problem to which you refer can occur in conditions below -15C or if the transfer lever has not been correctly moved from H to L (or vice versa) while using the hubs in auto mode, or haven't been disengaged properly when going back to 2WD ie reversed sufficiently (I've just read the manual).

But if one is still uncertain about the auto hubs, then you can always get a set of Nissan manual hubs from a wrecker for usually much less than AVM. Checked this out once for a friend who lived in the country, whose manual hub was way overpacked with grease and wouldn't lock and when taking it apart to clean, lost some bits and had to get a replacement.

I just had a look at the AVM site and the AVM hubs are not built like the Nissan ones. Check here: http://www.avm.com.br/products.htm. They have reduced the multiple springs with one spring (doesn't look all that flash either). The Nissan full manual hubs have no springs, but I can't see from the workshop manual whether the auto hubs have a spring, I suspect that they are cam activated when the axle starts to turn, but I don't know whether a spring (or what type - coil, spring or flat presure type) is required for deactivation.

Nissanofold,
The failure I saw was a GU Patrol, the auto hubs from Nissan are eight hundred odd dollars (list price) and the manual ones are the same price with just a few $$ difference, you can get them from the wreckers but all the ones I saw were more expensive than AVM and stuffed...
The condition in cold weather has very much to do with the transfer case oil and it is not down to -15c... Canberra dealers have the problem every winter...
The problem does not come from not shifting fully sorry I disagree on that one.
I do agree with you that the AVM hubs are not as good as the genuine manual Nissan ones.
Auto Nissan ones (even with the manual lock) work exactly the same as all the other ones and are just as unreliable and yes they do have a spring, the locking mechanism is not a possitive lock as per the manual units and you will notice that when you lock them manually then drive and unlock them (manually) they do not unlock until you reverse, give it a try!!
Don't get me wrong mine are still in one piece, never gave me any trouble (other than a few times when they would not disengage) and I did 150000kms (always locking them manually) before I removed them and installed AVMs, what I mean is (as previously mentioned) manual free wheeling hubs (of any brand) are more simple, more reliable and allow you to manouvre a heavy trailer in bitumen while in low range 2wd, much more convenient then the convenience the auto hubs provide...
In my opinion auto hubs are a step backwards but that is just my opinion...

The Nissan manual suggests -15C and also suggests that part of the problem is from hesitating when shifting from 2WD to 4WD. Not saying it won't happen in other circumstances, just what the manual suggests.

I always reverse to unlock the hubs after manually releasing them. Clearly the way they work is that there is a residual tension in the hubs after manually unlocking them, which requires the reversing. When manually locked, they are no different to a manual hub.

Having had nothing but manual hubs for well over 20 years, I really appreciate the Nissan auto hubs (my first MQ didn't even have selectable hubs). I've known quite a few with them who have never had a problem over many years. I guess it's how you use them that makes the difference.

150000kms so far on my GU and not the slightest hint of a problem with the auto hubs - I have also shifted on the fly from 2H to 4H at speeds up to 60kms on numerous occasions. I must admit though on my recent trip to Cape York I manually locked the hubs on on the OTL - but much of this trip was done in 2WD so I don't know if I got any benefit from doing this or not.