First of all: sorry for my bad english.
Now to my problem.
I have a 1999 blazer with a 236 tc np8. Yesterday i lost my 4wd. Control lamps on the 4 buttons looks ok. When i press 4wd hi it blinks 4-5 times and then lights is steady but still no 4wd. I havetested thevaccum swithch witch controls the frontdiff and its working.I can hear the tcmotor turn when i press the different2/4wd buttons. Changed the oil in the tcbut the old oillooks ok, no dirt in it. So my question, Is it the tranfer caseor the tc motor that is broken? I live in the north of swedenwith lots of snow so Ireally badly need my 4wd

 

I hope you put GM Autotrak 2 transfer case fluid in...

Have you checked to make sure that the front axle is actually engaging when vacuum is supplied to the actuator (located under the battery tray) when the solenoid on the firewall activates?

 

Yes...

I can hear and feel it in the car when i switch 2/4wd it makes a lttile clonk noise and i feel a slight push? twist? So I assumed it is working.

 

Now I have tested it some more. The frontdiff is working, When i use 4wd auto it works just fine but when i use 4wd hi itĀ“s engaged for 1-2secs and then i have only 2wd, the control lamp still indicates 4wd hi. 4wd low is not working either. I think thats strange,dosent the 4wd auto and 4wd hi do the same thing only difference is that in auto the car computer tells the tc motor to engage 4wd when it needs to.

 

Mine did this two years ago and I would up having to replace the Transfer Case Control Module. Little computer box under the Passenger front kick panel. The part cost like $380 at the dealer; couldn't find one used.

 

Ok, i have read something about reseting the computermodule by disconnecting the power and also check connection of the module so iĀ“ll try that first. Dosent that work IĀ“ll change it.