Hello everyone - great site!

My friend who is a Chevy Tech and I have been working on my blazer - a 99. We have been having some issues with the 4x4 and I want to get your views on it as well.

When you try to shift into 4x4 via the buttons, the lights do light up and stay lite on the button you press. You can also here the TCCM click when you press the button, and you can hear a slight noise from the transfer case on the shift. And there is no 4x4 service light either.

But, no power. At first we threw the truck on the lift to find that there was that vaccum plug, with 3 lines on it unpluged. It goes to the top of the transfer case I believe and is vents? I did research on it and thats what I found. Anyway, it seems who ever worked on it stuck something into one of the lines to block it off.. yeaaaa.

Well, we plugged it in and I did notice turning a corner in 4x4 the front tire griped and spun. Thats it. Its snowing now, and I am getting stuck all over the place. I had to leave the truck in the driveway.


What do you guys think? If it was vaccum to the actuator or the actuator itself, the lights would just blink and the TCCM would not shift into any 4 wheel gear, right?

Its weird. If the front tires griped once hear and there, could the actuator only be working just enough not to trip the light off but nothing more.

Since I am in this post, whats a good test for the actuator besides checking vaccum in the lines?

Thanks
-Jon

 

The actuator pulls the cable to engage the front axle it doesnt have anything to do with the t-case shifting or not just whether the front axle is engaged.
In my case the actuator looked to be working but wasnt pulling the cable quite far enough turned out vac line going to the actuator itself had a crack on the bottom side i just replaced all the vac lines while i was at it (chances are they all the same age and likely to go soon so figured may as well eliminate the issue completely but thats a personal choice)

 

Yea that sounds right if the actuator is pulling the cable a little bit but not enough, I am taking A. it would not engage the front axle and B. not trip off the lights?

I am gonna pull the battery and check the vac lines as well. I can still drive in 4x4, with my toyota pickup [:'(]

 

Do you have a 3-button switch or 4-button w/ auto4wd option?

 

3 Button Switch

 

The front axle will either be locked in or not. It only engages the front open differential, it does not lock both front wheels together. Depending on whether you have a G80 diff in the rear, it may be fairly easy to get stuck even in 4wd as without the G80, you could have two wheels spinning, one front, one rear. If you are getting one front wheel to spin, then your 4wd is likely working appropriately.

 

I believe my rear is G80, I have two tires spinning, I would have to double check. But even so, I do not believe this is the case for the front, as neither tire in the front even attempts to spin.

 

Oh, I took your statement that "we plugged it in and I did notice turning a corner in 4x4 the front tire griped and spun" to mean that you had power to the front wheels... Maybe it was a fluke...?

Have you tried manually pulling the cable at the actuator and locking it in with a pair of vice grips?

 

I was actuatlly going out to try that now, see if its the actuator which is cause the problem, then go from there, I will update. Thanks!

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Somethings up, I think. I checked the actuator, and followed the main vacuum line connected to it. It runs right up to the brake booster (not to the booster itself) and there are t- fittings connected to it. After further checking, I see after it connects to those lines, there is one line that runs I believe into the cabin, for the HVAC (?) and after that a line that is not connected to anything.

This line is short, it was leaning on the fender, is that for the vac tank?

*Combining Consecutive Posts*

So I got the cable, locked it in to engage.. nothing. only the rear was spinning, front was just hanging out just as if in 2 wheel drive

*Combining Consecutive Posts*

lol ok update again. Its pouring here so its making this hard to do. Anyways, I retraced the vac line from the acuator and it does go down to the transfer case. Then there is a line that comes up and meets with the t fittings by the brake booster, but ofcoarse I still have the leak there - I am trying to find where that hose goes to right now.

*Combining Consecutive Posts*

Okay,

So basically it looks like the vacuum could of been weak or shot, but when I touched that line I lost my HVAC controls so.

I am gonna just say that my vacuum lines did not have that much pressure, but should that be effecting the 4x4 - I tried to engage the diff from the actuator and clamped it once I had it about 1/2 towards the passenger side, but still nothing.

My understanding is that the vacuum as far for the 4x4 is for the actuator, correct? Even, lets say, the switch on the transfer case that handles the vacuum for the actuator line is bad, even if I manually engaged the diff, that should not be a problem...


*EDIT by swartlkk* - Please use the EDIT feature to include additional information in your post if another member has yet to reply. Consecutive posting in a short time span (<24hrs) is considered another form of Double Posting and is prohibited by forum rules.

 

Somethings up, I think. I checked the actuator, and followed the main vacuum line connected to it. It runs right up to the brake booster (not to the booster itself) and there are t- fittings connected to it. After further checking, I see after it connects to those lines, there is one line that runs I believe into the cabin, for the HVAC (?) and after that a line that is not connected to anything.

This line is short, it was leaning on the fender, is that for the vac tank?