Autohubs not disengaging in 2wd?

[jpfanner]

Has anyone had issues with their auto hubs not unlocking? Obviously living in Ohio we've been working our 4x4s out more than last year and my truck feels like there's more rolling resistance and you can kind of feel that very slight drive line vibrations like when driving in 4x4, but I know the transfer case is disengaged, I can feel it kick out when I put it in 2wd, and when I turn on drive pavement it doesn't buck the steering wheel. The only thing I can think of is the auto hubs aren't disengaging and still turning the front diff and drive shaft?? I didn't know if these become gummed up with age? This truck was from Baton Rouge so there's a chance the 4x4 might have only been engaged a few times. It has 157,000 on it and I bought it with 135,000. You think it's worth taking to a shop and taking the hubs apart and cleaning them out? Or should I just hope that weather above 0 degrees they'll work properly?

 

[AllGo'N'Show]

You can turn the manual hubs a few times to try and free it up, or pull them off and lube them up for good measure, my c-clips keep popping off mine so its good to check them every so often anyways. The back of the hub has a vacuum nipple, there is a seal in there but likely they wouldn't engage if that seal was messed up so I think your OK there in my eyes. Open your hood, does your vacuum pump run constantly? If so you likely just have a broken plastic hard line somewhere, the pump uses vacuum at all times whether engaged or disengaged, so the system has to be sealed properly to work properly. The most common breaks seem to be on the passenger side of the radiator fan shroud where they connect to the module attached to the shroud, two breaks in mine there and one a buddies there.

Here's a copy and paste from thedieselstop post;

Pulse Vacuum Hublocks

The ESOF system has a feature which allows the driver to override the vacuum-operated hublocks. When the front hublock dials are manually turned to the LOCK position, the hublocks are locked through the dial at all times, regardless of the position of the instrument panel MSS .
When the front hublock dials are manually turned to the AUTO position, the hublocks use an internal spring-locking mechanism that is vacuum-operated by the ESOF system, and are locked with the MSS in the 4X4 High or 4X4 Low position and unlocked with the MSS in 2WD position. Refer to Hublock in this section for additional AUTO hublock system operation.

Hublock Operation

With the hublocks in the AUTO position, the 4WD ESOF system uses timed vacuum sequences to lock and unlock the wheel ends when switching the instrument panel MSS between 2WD and 4WD modes. A high vacuum level (222 mm [8.75 in] Hg and greater) is applied to the hublocks to lock the internal spring mechanism that engages (locks) the hublocks for 4WD mode, and a lower vacuum level (114 to 184 mm [5.9 to 7.1 in] Hg) is applied to unlock the spring mechanism that disengages (unlocks) the hublocks for 2WD mode. The vacuum signals are supplied to the hublocks by system components, including the 4X4 control module, wiring harness, solenoid, vacuum harness and vacuum seals. As a first step in service, eliminate obvious items such as loose wiring connections, loose vacuum connections or damaged vacuum lines.

Hublock Engagement/Disengagement Time

With the hublock dials in the AUTO position, switching the instrument panel MSS to 4X4 High or 4X4 Low results in the high vacuum level being applied to the hublocks, which lasts for at least 51 seconds (including a venting cycle). The hublocks should engage during this time through the spring mechanism. Switching the MSS to 2WD less than 51 seconds after the MSS has been switched to 4X4 High or 4X4 Low will not interrupt the high vacuum level; instead, the lower vacuum level will be applied after the high vacuum level cycle is completed.

With the hublock dials in the AUTO position, switching the MSS to 2WD results in the lower vacuum level being applied to the hublocks, which lasts for about 15 seconds. However, the actual time required for the hublocks to disengage by spring force can vary considerably due to the effects of driveline wind up. Road bumps, vehicle speed, acceleration cycles or momentary reversal of direction can assist this process. Switching the MSS to 4X4 High or 4X4 Low always overrides the lower vacuum level cycle and results in an immediate high-vacuum level and in locking of the hublocks.

Manual Override

The AUTO hublocks have a manual override selector dial, which, when turned to the LOCK position, will keep the hublocks locked (through the dial) at all times, regardless of the position of the instrument panel MSS . (Always set both hublock dials to the same position.) If the hublock dials are manually turned from the AUTO to the LOCK position, and the high vacuum level is applied to the hublocks (by switching the MSS from 2WD to 4X4 High or 4X4 Low), the hublocks will be locked through the dial as well as through the internal spring mechanism. In this case, turning the hublock dials back to the AUTO position will leave the hublocks in (spring) locked mode until the lower vacuum level is applied to the hublocks (by switching the MSS from 4X4 High or 4X4 Low to the 2WD ). (This is not an issue if the hublock dials have been in the AUTO position and the MSS has been switched from 4X4 High or 4X4 Low to 2WD at least once.) Alternatively, the hublock mechanism can be reset to free mode at any time by turning the hublock dial from AUTO to LOCK to AUTO at least 2 times.

 

[jpfanner]

Thanks! I'll take a look at the hubs and check vacuum lines. I HATE vacuum actuated hubs but I guess at the end of the day it's the only way to have the convenience of shift-on-the-fly. :fustrate:

also, if anyone knows a good source to get and install a detroit locker, I'm getting one soon. This one-wheel-peel POS rear end is for the birds. Also, does OX or ARB make selectable lockers for the front axles of these trucks?

 

[AllGo'N'Show]

There is a big locker discussion going on somewhere around here, keep hunting and join in Lots of knowledge and lots of experience with all sorts of products, good info in that thread.
http://powerstrokearmy.com/forums/showthread.php?t=44281&highlight=locker


For your vacuum lines, if they are work trucks, off road trucks or rely on 4x4 and you keep breaking lines near the hub, dieselsite sells steel braided lines to product the exposed lowers more.

 

[Zmann]

just to make sure your hub is not disengaging like your assuming
you can grasp the axle shaft inside of the knuckle on either side of the truck and when in 4x2 you should be able to turn the axle shaft by the u joint

 

[eng53ine]

Also make sure someone didn't manually lock the hubs


02 ccsb, lariat, 7.3 auto, 4x4, 4" duals, 6637,zoodad

 

[jpfanner]

they're in AUTO mode. I'll reach in there today and see, either way I'm going to have my vacuum system checked out and have the hubs taken a part, cleaned and have gear oil put on them instead of heavy old grease.

 

[78f100]

We have broke a few launching them in 4hi and they stuck locked. I took them apart and got the splines freed up but they kept doing it so we replaced them.

 

[3brorce]

I have the opposite problem. My hubs dont want to auto lock when in 4wd. Have to put them is manual for 4wd to work it seems.

 

[webb06]

I have the opposite problem. My hubs dont want to auto lock when in 4wd. Have to put them is manual for 4wd to work it seems.

Prolly just need lubed so they'll slide when being pulled in by vacuum

 

[AllGo'N'Show]

We have broke a few launching them in 4hi and they stuck locked. I took them apart and got the splines freed up but they kept doing it so we replaced them.

Just the outer auto hub broke no other damage?