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Left automatic hub not reliable after rotor replacement

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Left automatic hub not reliable after rotor replacement

Old 02-02-2019, 03:05 PM
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Left automatic hub not reliable after rotor replacement

After having the front brake rotors replaced on my '87 4Runner with MT5, the left automatic hub isn't working correctly, and I'm wonder how to fix it.

The right hub engages normally, shown by rotating the half-axle forward, it engages within a turn. The left does not, and only reliably engages if I rotate the half-axle in reverse. Is it possible they put the automatic hub back in with something reversed, perhaps?

Further, if I get both hubs engaged, then switch to 2H, sometimes the left hub disengages and then I can hear it banging about once per revolution while driving slowly. My guess this is because with the right hub still engaged, the axle now turns backward on the left side which is the direction it seems responsive to. But the speeds and direction of rotation aren't matched, so the hub can't lock in. Thus the bang.

Any ideas?

If it's an easy fix, then I'll just do it myself. Otherwise, I'll give it back to the mechanic to deal with, but there's always risk with that, and I'd like to go in knowing the fix.

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Old 02-02-2019, 05:16 PM
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could have damaged the auto hub brake/spring mechanism. probably the spring is twisted inside the hub, and no longer wound correctly within the hub brake drum. open it up to see.

Last edited by wallytoo; 02-02-2019 at 05:18 PM.
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Old 02-03-2019, 10:55 AM
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Originally Posted by wallytoo View Post
could have damaged the auto hub brake/spring mechanism. probably the spring is twisted inside the hub, and no longer wound correctly within the hub brake drum. open it up to see.
How easy is it get to that examination point in terms of dismantling effort and special tools required?
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Old 02-03-2019, 12:30 PM
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Very few trucks originally equipped with these auto hubs seem to still have them installed.

I have owned several that came from the factory with them and all had been retro-fitted with manual Aisins, or Warns.

Are they weak, or just finicky to service??
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Old 02-03-2019, 02:14 PM
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Originally Posted by Blueman View Post
After having the front brake rotors replaced on my '87 4Runner with MT5, the left automatic hub isn't working correctly, and I'm wonder how to fix it.

The right hub engages normally, shown by rotating the half-axle forward, it engages within a turn. The left does not, and only reliably engages if I rotate the half-axle in reverse. Is it possible they put the automatic hub back in with something reversed, perhaps?

Further, if I get both hubs engaged, then switch to 2H, sometimes the left hub disengages and then I can hear it banging about once per revolution while driving slowly. My guess this is because with the right hub still engaged, the axle now turns backward on the left side which is the direction it seems responsive to. But the speeds and direction of rotation aren't matched, so the hub can't lock in. Thus the bang.

Any ideas?

If it's an easy fix, then I'll just do it myself. Otherwise, I'll give it back to the mechanic to deal with, but there's always risk with that, and I'd like to go in knowing the fix.

I'd take it back to the shop. I've always just changed autos over to manual lockers, for what it's worth. Yes, you have to get out to lock them but they are simple and reliable. There are many types of "auto" locking hubs. I'm not even sure what would have come on your truck but when you start getting into electronic ones, vaccuum operated ones (more likely on yours), it can get more complex real quick.
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Old 02-03-2019, 04:28 PM
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Originally Posted by millball View Post
Very few trucks originally equipped with these auto hubs seem to still have them installed.

I have owned several that came from the factory with them and all had been retro-fitted with manual Aisins, or Warns.

Are they weak, or just finicky to service??
the auto hubs on my 86 4runner (bought new in 86) went out after less than 10K miles. There is a plastic piece inside that doesn't last long at all. Replaced hubs with manual and never had any issues for the next 100K until I traded in the truck in 91.

OP get with the shop that did the work, sounds like the screwed the pooch
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Old 02-03-2019, 05:43 PM
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I'm not planning to switch away from the automatic hubs, but I'm fully aware of that option.

Note that these are different than the ADD hubs that use vacuum control -- those came in later models.

My questions are simply:
- how hard is it to pull the hub to inspect it for an issue like I'm seeing?
- has anyone seen this behavior before, and know what fixed it.

Yes, of course I realize that taking to the shop that worked on it last fall is an option, but rarely is that process as simple as it sounds so if it's less than an hour or two of work, it's simpler (and faster) for me to fix it myself. Thus my pinging the wisdom of other Gen1 fans out there who might have some insights.

thx
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Old 02-03-2019, 06:23 PM
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[QUOTE=Blueman;52417523]Note that these are different than the ADD hubs that use vacuum control -- those came in later models.[/QUOTE

Yes. there are truly no hubs at all on ADD equipped trucks/ Only one piece steel drive flanges, and the half-shafts turn all the time.
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Old 02-04-2019, 04:49 AM
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Originally Posted by Blueman View Post
How easy is it get to that examination point in terms of dismantling effort and special tools required?
pretty simple. remove the cover, pull cover. remove snap ring.

loosen the six hub mounting bolts. solid tap the studs using a drift and hammer, until the cone washers visibly begin to slide outwards. remove locking hub assembly. inspect the insides of locking hub assembly that you just removed. is there a piece of metal all twisted up in the outer cavity?
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Old 05-28-2019, 04:30 PM
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Okay, so it sounds like they found a broken spring inside -- anyone know where to get replacement springs? Or since people seem to hate these hubs (that I like), care to send me your old spring?


Okay, so it sounds like they found a broken spring inside -- anyone know where to get replacement springs? Or since people seem to hate these hubs (that I like), care to send me your old spring?
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