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Auto hubs

5K views 4 replies 3 participants last post by  Bklyn.X 
#1 ·
After changing broken CV (had both hubs off) I had a sticky hub.
Took it completely apart,plastic piece looked fine. Put it back together and now it's working fine.

Now to my question........

I've been a mechanic,gas turbine tech and lastly a machinist for the last 25 years but for the life of me I don't understand how these things work.
Not a dummy but I just don't see it. Don't see how rotational torque from the CV shaft makes it engage.

Anybody care to explain? (TJ hoping you'll chime in)
 
#2 · (Edited)


There is a spring within the internals of the hubs keeps the engagement teeth of the hub separated allowing the wheel to “Freewheel” when it is not under power from the differential.

The “fixed cam assembly” is “fixed” to the knuckle spindle. It does not turn with the wheel or half-shaft so it is the anchor within the hub enabling the hub to distinguish the half-shaft moving.

When you put the transfer case in 4wd the rotational power, transferred out to the hubs via the half-shaft, causes the “fixed cam assembly” mechanism within the hub assembly (transforming the rotary motion of the half-shaft into linear motion) to push (overpower) the spring, allowing the teeth of the locking the hub to engage.
The “fixed cam assembly” can not “tell” if the wheel is turning (torque from the road pushing the wheel) before this happens because the teeth of the locking the hub are not engaged until it does (refer to 1st sentence).

They stay engaged until you go from forward to reverse and the “fixed cam assembly” (transforming the rotary motion of the half-shaft into linear motion) releases the spring that then pushes the teeth of the locking the hub to the unlocked position. In 2WD (receiving no rotational power) the spring will cause the teeth to stay disengaged. In 4WD the hub assembly (receiving rotational power) will disengage and re-engage very quickly.

Rocking your auto hub equipped truck back and forth is what usually blows a hub (disengaging and re-engaging while receiving rotational power).

This is why folks change to a Manual Hub; it does not depend on rotational power from the half-shaft, it is always locked or unlocked.
 
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#3 ·
Okay, I’m just posting the following info in this thread rather than in each of the many threads asking about our auto hubs. I wanted to update you folks as soon as I found out this information I got from a friend of mine.

He needed to replace his Auto Hub and was able to order the “Fixed Cam Assembly” from his local dealer for $83!

This is apparently a new thing. The “Fixed Cam Assembly” is now called a “Thrust Washer”;

Nissan Lookup code 40256D
Nissan part number 40218-8B400

This part will not be around long because, as you know, the Auto Hub (40260-9Z500) has been discontinued. So if ya need one and can still find it act fast.

My friend also bought a new Auto Hub Assembly! It a bit different than the old one in that the “Fixed Cam Assembly“ is built in and therefore not serviceable and a PITA to line up correctly so it fits flush. It uses the same hex screws as our old one, works in the same way and according to my friend “works perfect”.



The part number for this new Auto Hub Assembly is 40260-1S700 and will come up in a Google search. I’ve seen it discontinued, in stock online for $323.39 (YIKES!), on Amazon for $173.63 and for $160.46 on ebay where my friend got his;

http://www.ebay.com/itm/252039017682?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

I’d act fast if I wanted any of this, no telling when these links will be no good and the parts, like our old Auto Hubs, will disappear.
Good luck!
 
#4 ·
I have gone thru that whole mess with Nissan not having the fixed cam assembly etc. the part doesn't exist anymore.

I'm kinda confused, according to your diagram above the thrust washer is for a manual locking hub, not a auto locker hub. Are the saying the thrust washer will work as a direct replacement for the fixed cam assembly on a auto locking hub?
 
#5 · (Edited)
Are the saying the thrust washer will work as a direct replacement for the fixed cam assembly on a auto locking hub?
No.

What I’m saying is that this is new to me. My friend needed to replace that plastic POS in his Auto Hub and was able to order the “Fixed Cam Assembly” from his local dealer for $83. Before this time I did not think you could buy it separate from the Hub assembly. He said that the “Fixed Cam Assembly” pictured in the diagram above is now called a “Thrust Washer ” (different than the thrust washer pictured in the diagram above) by Nissan and is available through Nissan until they run out of them;

Nissan Lookup code 40256D
Nissan part number 40218-8B400

He bought that part using that part number. When I asked;
Sorry to keep asking but I want to be sure I understand. Is Thrust Washer aka Fixed Cam Assembly:
Nissan Lookup code 40256D
Nissan part number 40218-8B400.

This part;


Exploded picture of the same part;


Thanks
He said;
Yes based on ordering the part at my local Nissan dealer that part in the picture is what came in based on the part numbers you have listed above.
I am passing that info on to you in the hope it might help.
 
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