'94 DLX 4x4 manual transmission. Man when it rains it pours. I don't know if this is related to my other electrical problems (see thread a few posts down on gauge cluster burnout and general electrical issues) but my truck has developed a squeal that I have tracked down to the drivers side locking hub I think. In 2 wheel I have a intermittent squeal that seems to be getting worse and today I had the hub lock/unlock while driving at a slow speed causing 3 loud bangs. The squeal sounds like a angry squirrel, or similar to a VW bus I once owned with a dying speedometer except louder. The squeal only happens in 2 wheel drive although it may have happened once in 4 wheel, unsure. I disconnected the vacuum hoses from the locking hub actuator and the squeal continues in 2 wheel, seemed worse. It completely goes away in 4 wheel with the vacuum hoses disconnected so not really in 4 wheel since the hubs don't lock, thats how I'm driving it now. I'm worried that this may cause problems with the transfer case engaged but not delivering power to the front wheels. I found a wrecked truck a guy is parting out thats a exact match for my truck except its a automatic. I'd like to pull any parts I may need now but I need some help on what exactly this problem is and if its related to the electrical problems I described in the other thread. Today when the locking hubs engaged the 4x4 light did not light, before the relay under the dash that is involved with the transfer case started clicking rapidly, I have since replaced that relay with a good used one. I took the case off the old relay it looked fine but replacing it seems to have helped.

Any ideas? Am I damaging anything by driving with the transfer case engaged but the hubs not locking? The truck seemed to drive fine this way, acting like it was in 2 wheel drive which I guess it is.

Probably unrelated: I found a bad tie rod end on the same side that I will replace soon.

Thanks.

EDIT: I did a bit of research and I think my truck has ADD hubs, not auto hubs.

 

Locking hubs vacuum actuator??? Transfer case engaged, but hubs no locking???

You do not seem to have a good grasp of how your trucks front drive system works.

Sounds like you have an ADD (automatic differential disconnect) system.

This system has NO LOCKING HUBS,

It uses permanently connected drive flanges at the front wheel hubs. This means that the front half-shafts turn with the front tires, regardless whether in 2WD, or 4 WD.

When the transfer case is selected to 4WD, a switch on the transfer case shift rail sends a signal to a vacuum switching valve that is supposed to send vacuum to an actuator
that shifts a collar in the front differential that connects the drivers side axle to the differential.

Have a look at the Factory service manual and familiarize yourself with how this system operates. your noise may be a half-shaft, or front spindle lubrication issue.

The 4x4 light will only light when the ADD collar has physically moved into the locked position.

 

Ya I don't really have a good grasp on it all, since its never broken. I did some more research and now I know more, please no bully.