I have a 2000 Blazer w/ the Auto 4wd NP8 Transfer case. I am getting conflicting info about problems with the transfer case and front axles. First the front axles don't disengage, I was told they put vacuum to the acctuator and it did nothing? Should the fron axles be free completely in 2hi? I was told it was an AWD like system and that was the way it should be, which conflicts with the story I got from the other guy. The front drive shaft spins in 2hi also and I was told the clutches would be shot in the transfer case and need to be rebuilt, but I see online that a fluid change may free this up or could this be from the front end? Thanks in advance for any help.

 

The clutch in the NP236 transfer case is preloaded. The front driveshaft will always turn regardless of the mode selected.

Now, with the front end jacked up in the air, can you spin one wheel without the other wheel spinning opposite? If the opposite wheel spins, then the front axle is engaged. This is not good to be driving on.

If you decide to change the fluid in the diff, only use GM Autotrak II fluid. Bad things can happen to your transfer case if you use other fluids regardless of what the salesman states.

 

Thanks for the reply and yes, with the front off the ground if I spin one wheel the other spins in the opposite direction. So, I have been told the transfer case is bad because the front drive shaft is turning in 2hi. I am glad to hear this is not a problem. I will go ahead and change the fluid with the GM AutoTrac II Fluid (sounds like that is not a bad idea to go ahead and do).

Now, for the front axle, I have read many posts about the vacuum actuator under the battery and a release cable. How do I check these parts? I find the actuator at NAPA, but don’t see any cable that is serviced?

Thanks again.

 

The cable should move somewhat freely. If it does not, then the cable may be froze up. You can lubricate it with some penetrating oil and work it to free it back up. You may have to remove it to free it up properly. This item may be a dealer only part or you may be able to find a good one from a junkyard. If yours is kinked in any location, get a replacement.

 

Thanks again for the help. Why I'm in the mood and in the area I will service the front end. Should I use the AutoTrac II Fluid in the ffront end also or is regular gear lube fine?

Thanks.

 

Front takes 80w90 GL5 gear lube or 75w90 synthetic.

 

Thanks once again for all your help. I have found the cable shield towards the bottom end was broke off and the cable was completely froze up. I will get this replaced tomorrow, almost bought the cable tonight at the dealership when I picked up the AutoTrak II for the transfer case. Hopefully there is no damage done in the front end.

I was told at a Transmission Shop that since the front drive shaft is spinning, the clutches are burnt up and the transfer case needs rebuilt. Above you mention that the clutches are suppose to spin all the time. How do I know if there is an issue with the transfer case?

Thanks once again for all the help.

 

If you get bad binding while turning in 2HI or Auto4wd, then the clutches are bad in the transfer case. If not, then don't worry about it.

 

When you say bad binding...

Mines stuck in the auto4wd mode that you commented on before, not all the time but sometimes during slow sharp turns the steering wheel seems to shudder.

 

If it is not all the time, I do not think you have anything to worry about. My AWD Rainier does this from time to time when the TCCM detects that it should lock up the front axle.