Autolock Hubs - I Wonder...

[Bee Elzebub]

...If anyone can explain how these widgets stay locked in, if you reverse in 4WD on slippery ground?

I ask, as the little sticker on the sun visor says "to disengage hubs, engage 2WD, then reverse a short distance" (something like that, anyway)... So hwo do the hubs stay locked if you're reversing on mud/snow, etc? :nenau

With snow forecast for this winter (again), I'd just like reassurance that the bloody hubs'll work, if I slither into a hedge or summat!!!

 

[makeitfit]

While in 4wd they stay engaged forward or backward :thumbs It's only when there's no drive from the shafts that the "dissengaging" thing can happen thanks to a little spring and cam affair.

 

[Bee Elzebub]

Aha! Thanks for that, couldn't figure out how the buggers worked, that's all! I had a vague idea that they worked like a one-way starter-type 'clutch' as used in motorcycle engines; maybe, maybe not...

Mystery cleared, thanks very muchly!!!

 

[solarman216]

While in 4wd they stay engaged forward or backward :thumbs It's only when there's no drive from the shafts that the "dissengaging" thing can happen thanks to a little spring and cam affair.

Have to contradict you on this one, when you change direction they disengage and then re engage, that is why you need to do it gently, easy to prove, just jack up one front wheel and turn the prop forwards it will engage, now turn the prop back it will dis engage and if you keep turning will engage again, Rick

 

[makeitfit]

Fair play, I'll have a play when I remember:thumbs
Never noticed when driving it in the ruff either :augie so it's pretty damn quick and tough. I knew to be gentle when first going into 4x4 but never been kind to it after that :naughty

 

[lacroupade]

Have to contradict you on this one, when you change direction they disengage and then re engage, that is why you need to do it gently, easy to prove, just jack up one front wheel and turn the prop forwards it will engage, now turn the prop back it will dis engage and if you keep turning will engage again, Rick

Probably true but surely not relevant because as Pete rightly says, once drive is engaged with the gearstick the jobs done. The hubs are ONLY under any strain when actually engaging or disengaging drive....once its in or out, no amount of reversing etc.. puts any strain on them. Thats why its a popular fallacy that the springs can be busted by excessive offroad activity while in 4WD - which of course is totally untrue.

 

[solarman216]

Probably true but surely not relevant because as Pete rightly says, once drive is engaged with the gearstick the jobs done. The hubs are ONLY under any strain when actually engaging or disengaging drive....once its in or out, no amount of reversing etc.. puts any strain on them. Thats why its a popular fallacy that the springs can be busted by excessive offroad activity while in 4WD - which of course is totally untrue.

once drive is engaged all that means is the front diff is being driven but same applies, if driving forward stop and engage reverse the hubs will unlock and then re lock again, pretty quick I admit but the do unlock, so I can see if you really give it some welly there must be the possibility of doing some damage during relocking, once locked no problem, Rick

 

[lacroupade]

once drive is engaged all that means is the front diff is being driven but same applies, if driving forward stop and engage reverse the hubs will unlock and then re lock again, pretty quick I admit but the do unlock, so I can see if you really give it some welly there must be the possibility of doing some damage during relocking, once locked no problem, Rick

I'm going to argue that because I don't think its 100% correct. Its always been my understanding from talking to a number of technical people that once the half shaft is engaged, whether you're reversing or driving forward, the snap rings are OUT of the equation until/unless you disengage 4WD with the lever (at the diff one assumes).

I mean logic alone tells me that, knowing the requirement for 'rocking' a vehicle with the gearbox on a difficult situation, no 4x4 manufacturer with Nissans lengthy experience is going to make a pissy little tempered steel ring such an obvious point of failure are they?

In fact isn't there some sort of collar arrangement that locks the half shaft to the hub?

 

[Thomas-the-Terrano2]

surely its the half shafts turning that induce the lock.

so once in forward or reverse they remain locked

can prove this as if lock 'em for some action then go
into 2wd on lever, front end remains locked and ready
akin to fixed hubs.

on many a trip we've had those reversing at end of lanes
to my suprise as will be locking again in say few miles.

after all the ecomomy of fwh's isnt going show and yet the
car IS in 2wd defined by lever, not hubs or tell tale on
dash.

so sure reverse then with lever in 2wd they release as
half and prop shafts are free too.

also 4wd operates even in reverse if thats the first direction
chosen. cant really have one direction less able than other.

 

[lacroupade]

surely its the half shafts turning that induce the lock.

so once in forward or reverse they remain locked

can prove this as if lock 'em for some action then go
into 2wd on lever, front end remains locked and ready
akin to fixed hubs.

on many a trip we've had those reversing at end of lanes
to my suprise as will be locking again in say few miles.

after all the ecomomy of fwh's isnt going show and yet the
car IS in 2wd defined by lever, not hubs or tell tale on
dash.

so sure reverse then with lever in 2wd they release as
half and prop shafts are free too.

also 4wd operates even in reverse if thats the first direction
chosen. cant really have one direction less able than other.

The other reason I'm confident this is the case is that having owned two automatics I know that the old 'rocking on the gearbox' trick is far easier with them than on a manual....its literally just a case of rowing the gear selector from D to N and back again; something I've done loads of times and which would have minced the poncey little snap rings in milliseconds had it been deselecting 4WD somehow. So until someone proves otherwise with diagrams and explanations, I'm sticking with the perceived wisdom that the snap rings are ONLY active and under stress when initially selecting and engaging 4WD and when disengaging by deselecting with the 4WD lever AND reversing at least a metre. Other then that they are doing nothing :nenau

 

[solarman216]

Sorry but I stand by what I say they unlock and re lock on change of direction, it is so easy to prove, just jack the front up and turn the half shafts first one way then the next, Rick

 

[Thomas-the-Terrano2]

well i'll pass as got fixed hubs....till i get manuals lol

 

[lacroupade]

Sorry but I stand by what I say they unlock and re lock on change of direction, it is so easy to prove, just jack the front up and turn the half shafts first one way then the next, Rick

That may be the case but I don't believe for a minute that involves the snap rings......I mean common sense says that would just be plain stupid because they are weeny little pieces of shite and no engineer with even half a brain cell would design such a ridiculous point of failure.....

 

[solarman216]

I do not believe I said anything about snap rings, I was just letting everyone know that they unlock and relock on change of direction, Rick

 

[lacroupade]

I do not believe I said anything about snap rings, I was just letting everyone know that they unlock and relock on change of direction, Rick

In that case we are violently agreeing LOL

Having said that one of your posts upstaitrs does say you can see how damage can occur during relocking, which imples to me that you think the snap rings ARE involved. I say they aren't. That would be monumentally stupid engineering.

 

[solarman216]

by snap rings I guess you mean the circlip that holds the shaft in place, or are you referring to something else, I must get round to dissecting one of these hubs sometime, Rick

 

[lacroupade]

by snap rings I guess you mean the circlip that holds the shaft in place, or are you referring to something else, I must get round to dissecting one of these hubs sometime, Rick

Not sure Rick cos I've never dismantled one, but they do break occasionally....they are just a weedy medium spring circlip-type thing essentially. I've done 100s of 000s of miles in T2s, a fair bit off road, and never had a problem with them.

If you get time it would be interesting to see what you think when you've dismantled one....as I say, I can't see any engineer making them an integral part of the drive and I've always understood that they are only ever under load for a millisecond when you first engage 4WD after which they are out of the frame for obvious reasons.

 

[solarman216]

Auto hub in bits

well people, dissected a hub today, interesting bit of kit, and really quite robust, shame the first one I split was in a rather poor shape as it had bits missing and some damage due to poor assembly, so I had to take a known good one of mine to see what was missing, any way this picture is of the innards minus the outer assembly, it is in the free running setting, this whole section with the outer casing remains stationary as it is fixed to the shaft, the crucial bit is the cone on the extreme right which mates with its opposite fixed to the hub which is rotating, when the shaft starts to turn there is enough friction to start the cam ring turning and as soon as that happens pressure increases and sufficient friction is available to complete the cam ring turn which forces the dog clutch into its mate on the wheel hub.

 

[solarman216]

this pic shows the hub in its drive position, shaft rotating clockwise looking from the dog end.

 

[extreme-4x4]

so are you still saying it disengages between forward and reverse rick ?
now you have had a good look