explain how i dont have 4wd

[hansj3]

My 00 silvarado is used to tow, get stuff from home depot, and as a back up for me and my gf. Its a good truck, has a rebuilt trans that shifts smooth and plenty of power, but 4wd won't engage.

On top of that the g80 won't lock up, but thats another problem

The 4wd switch works well enough to get the actuator into 4
The axle mechanically works to lock up, in 4 the front driveshaft won't spin
And the transfer case switches into high and low

What am I missing to check? why wont it work?

 

[BreakerBreaker]

Preliminary search points to button module, actuator, fuse, or some kind of sensor.

http://www.gmtruckclub.com/forum/threads/4wd-not-engaging.20340/

Ironically enough, my 4WD will not engage either, but my vehicle is not comparable to yours. I need to start from scratch in figuring out mine. Trans works perfect, though.

 

[Snoman002]

My guess is front axle. If you engage 4wd the front axle will be locked by the transfer case, the axle could still not be engaged.

Pick up passenger side front wheel(if the diff is on drivers side) and see if it spins freely when 4x4 is engaged, if so it's the actuator.

 

[NHGUY]

Gotta love electronic/vacuum 4wd.I guess manual hubs/floor lever wasn't attractive enough to grab enough "borderline" shoppers to the 4wd fray.Parts stores sure love to sell all the parts these require....

 

[hansj3]

The front axle is fine, the actuator is fine and the xfer case does high and low. What else is there? I guess I'll start with the switch, as its the only kinda broken thing

 

[SwampSurvivor]

I'd start with the switch.

If either the axle *or* the transfer case is working correctly, the front driveshaft will spin. IE - the transfer case isn't going into 4wd, but the axle is engaging, the axles will drive the differential which will spin the driveshaft. But the driveshaft won't be "connected" to the power.

If the axle isn't working, but the transfer case is going into 4wd, the driveshaft will be spinning and receiving power from the trasfer case, just not turning the wheels.

 

[hansj3]

Update:

I just lifted the truck off the ground and all four tires spin... kind of.

The rears are normal sans locking action

The fronts will spin and they have differential action if one side is held. However if they are both held the wheels won't spin and neither will the drive shaft. [censored]? I've never seen a transfer case have clutches, but that's kind of how it feels( like a slipping clutch)

Has Anyone ever seen this?

 

[zrxkawboy]

Does the transfer case have an Auto function?

 

[Dyusik]

My cousin went through 3 solenoids on the t case in a short order, and we hardly ever have snow or ice. This was a 99 Tahoe, I'm guessing the hardware is the same.

 

[hansj3]

Yeah its got an auto 4wd

 

[zrxkawboy]

Originally Posted By: hansj3
I've never seen a transfer case have clutches, but that's kind of how it feels


I believe that the 'case with the Auto function does have clutches.

 

[meep]

it's the t-case if the front driveshaft is not firmly engaged.

the free-wheeling spinning you describe does not necessarily describe clutch contact either--- that could just be internal friction in the t-case keeping them spinning together.

try 4 PT (part time) or 4L if the selector has it. If it's ONLY an auto-AWD then chances are you're gonna have to get into that tcase to see what's going on.

Many will immediately point out the actuator on the front axle as they have a reputation for going bad.