4x4 issues

[yuflesh]

Hey guys,
here is a mistery one. Enlighten me if you can. My 4x4 is acting up and Im trying to figure it out. First the light in the cabin died (Ive checked the bulb, and its good). Mind you, it would engage into 4 wheel drive. Now it won't engage period. Even if you try 4Lo. Front shaft does lock in. Ive gone under the truck and could not turn it by hand.

Any ideas / suggestions / quick things to check before I go to the shop?

Its a 91 3/4 ton light duty.

Thank you

Marko

[diesel65]

Sounds like your thermal actuator has gone south, without the actuator the front differential won't engage and turn the 4X4 light on.

[NH2112]

Are you saying that the axle disconnect IS engaging, but that no power is getting to the front wheels? If so I'd say it's either something broken inside the transfer case or stripped splines on the front driveshaft.

[murphyslaw]

ok hijack........

my 4x4 hasnt been working so just now I pull the therman acuator get some jumpers hook it to 12v and it extends just fine and i squez it and it pushes harder. ok that works. turn on the key(to run, glow plugs are cycling and everything) put it in 4h craul under and hook the dm to the plug and there is no voltage. the chiltons dosnt mention anyware in the thing about the 4x4 engagment system. is there a fuse someware im missing? im assuming there is a switch on the TC to tell the axel to lock? im at a loss here and would really like this to work so i can go hunting tomorrow.

[Robyn]

There is a switch on the T case that feeds power to the Thermal actuator which once activated engages a switch on the front end that does several things.
1- It turns on the light in the console
2- It turns off part of the ABS system in some models
3- Possibly other things too.
Check the switch to make sure its working and if there is power to it.
Let us know

Robyn