1999 s10/blazer LS 4x4 4.3L (3 button 4 wheel drive)

im not 100% sure my 4 wheel drive is really working
i hear it make noises when i switch from 2hi to 4hi and when i put in nuetral and goto 4lo i also hear noise

when i goto a dirt road and put in 4hi or 4lo and i put on brakes a little my front tires dont turn and my rear tires turn

01 when in 4hi (or) 4lo should my front tires turn when my back tires do even when my brakes are applied?

i check to make sure the vacuum switch on top of the transfer case was working by removing my battery and taking out the battery tray and starting the blazer and switch from 2hi to 4hi and i can see that diaphram pulling the cable correctly
i then shut the car off and manually pulled the cable a little just to check movement and i think it felt ok to me (it wasnt jammed i mean it moved a little)

02 what does the other end of that cable goto?
03 any diagrams or info on what to do when the vacuum switch and diaphram are working ok?

maybe my 4x4 mode is working but when my brakes are the front tires dont turn and my rear tires do....

any help would be great of course
thanks

 

Start the engine, select 4WD HI, jack up just the right front wheel. If you can turn it by hand, 4WD is not engaged.

To answer your questions:
1) Depending on which differentials you have, at least one front and one rear wheel should have power.

2) The cable goes from the axle actuator under the battery tray, down to the right front axle tube. Inside the tube there is a clutch mechanism that connects the right front axle to the differential.

3) Yes, but get it diagnosed first, then we'll deal with that if necessary

 

right front = passenger front?

 

Correct (left= drivers, right=pass)

 

raised the RF tire (left it in park) and in 2HI and i could rotate tire freely and it didnt make any noise

put it in 4hi and could still rotate the tire but it makes clicking noise as i rotate

does this mean the fork is not engaging all the way?

also if i drive down the dirt road in 4hi i hear that same noise when i go slow (less then 15MPH)

if i go faster i cant hear because of the gravel hitting the car and i have a bad muffler

so it prob still makes that clicking at higher speed too

 

check the diaphram under the battery, might be bad and you can check the pull cable there too, if it's sticking time to replace it.. if it's been doing this for a long time though, you might have messed up the gear in the diff.

 

i started the blazer up and removed battery and tray and i can see the diaphram
when i put it in 4hi it move the cable and the diaphram stays pulled back correctly

when i turn car off i see the diaphram it goes back to normal

so i think that is working ok

what else you think it could be?

 

Perfect. This means the axle clutch is releasing completely.

The axle clutch is not fully engaging the axle to the differential. What you're hearing is the axle teeth trying to mesh with differential, (gears grinding).

It is not pulling the cable far enough.

NOT normal. When you turn the engine off while in 4WD, the diaphragm should not move. If it does, there's a vacuum leak. That's probably why the cable isn't pulling far enough too. The most likely problem is the transfercase vacuum switch is leaking.

 

great info and thanks

i took the manifold main vacuum line and capped it (this is the line that would normally goto transfer switch, cruise and heater)
basically i just plugged it right before the check valve so nothing should be getting vacuum

i then started the car up and got inside and i still can hear some noise (like alot of people say) coming from behind the heater controls (which usually means that vacuum switch that has the 3 hoses) but like i said i disconnected all that stuff and just have the main manifold vacuum line plugged before the check valvei
so what could that noise be i wonder?
it might not even be related but like you said it prob means i have a vacuum leak somewhere when that diaphram under the battery gradually returns to normal position when i turn the car off

so i kept hearing that noise from where it sounds like behind the heater controls so i started isolating the different vacuum systems and it still made that noise so i decided to plug the manifold vacuum line before the check valve so (nothing) should be getting any vacuum at all

not sure what that noise is...

 

Cruise doesn't use vacuum, it's all electronic Anyway, a vacuum leak in any line after the source, (intake manifold near the PCV valve) could cause HVAC and or 4WD problems. You'll need to figure out which system has the leak, HVAC or 4WD. The HVAC line goes to the firewall and into the cab. Your 1999 has an electro-vacuum switch mounted to the firewall under the hood for the 4WD system. It has a vacuum line and an electrical connector and it's close to the center of the vehicle. If the vacuum switch is leaking, or not able to seal the actuator from the vent, the axle actuator might not get enough vacuum to pull the cable far enough to engage the axle. Can't remember for certain on a 1999 3 button system, but there may also be a vacuum switch on the transfer case. If it does, they are known to leak, very common problem.