I was plowing snow this morning and the 4wd on my 01 Jimmy seemed to work fine. I shut it off for a few minutes to move the other vehicles so I could plow there and when I restarted the Jimmy 4wd wasn't working. I manually pulled the actuator cable that engages the front axle and held it with vice grips but it still won't engage the front wheels. Any suggestions would be greatly appreciated.

 

What are the status lights in the pushbutton controls doing? 4 button auto or 3 button 4wd?

 

I have a 3 button 4wd
The buttons appear to be working proper
4 hi lights when I press it
as does the 4 lo in neutral and 2 hi lights when its pressed
When I press 4 lo it feels like it's trying to engage but I still don't have 4wd
When 4 hi is pressed I hear the click but nothing happens

 

Sounds like front axle is not locking in.

Jack up passenger front wheel off the ground.
Start engine and select 2WD (trans remains in park) - note how easy you can spin the tire by hand.
Now select 4WD. With the 4WD status lit solid, you should not be able to turn the wheel.
Report please.

 

ok... I checked like you suggested
the front wheel turns in both 2 hi and 4 hi
I also checked the drive shaft running to the front and it will not turn in 4 hi
I'm open to suggestions
And thank you so much for the help

 

It's doing just as you said
the wheel turns in both 4 hi and 2 hi
any ideas as to what the problem might be?

 

Based on the assumption that you could manually spin front driveshaft during the test above when in 2WD (engine running, trans in park) but not when in in 4WD, the TC is actually going into 4WD. Disconnect hose at front axle actuator and test for engine vacuum with a gauge in 4WD while running. Report please amount of vacuum measured.

If low or no vacuum, then vacuum switch on TC or hoses are bad. If full engine vacuum is seen, then problem is in either the actuator or the locking mechanism itself inside the front axle. We can cross that bridge when we come to it.

 

I just pulled the cable manually from under the battery with the Jimmy in park and the engine running in 4 hi but the passenger wheel still turns? What else should I check?

 

How can I check the locking mechanism?

 

How far does the cable pull (measure how far you can pull it AFTER removing vacuum hose). I'm still waiting for the vacuum reading. It's sounding like internal in the front axle.