4x4 problem on a blazer 96

need help!!
i have a 1996 blazer and i put the 4x4hi and the low on but the 4x4 don't work.
can enyone help me??

need help!!
i have a 1996 blazer and i put the 4x4hi and the low on but the 4x4 don't work.
can enyone help me??


Most common reasons

1. Vacuum leak

2. front diff actuator: http://www.automotiveforums.com/vbulletin/showthread.php?t=498812

3.transfer case vacuum switch

Most common reasons

1. Vacuum leak

2. front diff actuator: http://www.automotiveforums.com/vbulletin/showthread.php?t=498812

3.transfer case vacuum switch

thanks for the info!!
but we just changed the vacuum under the batery and it wasn't that.
but were can i find the front diff actuator and the transfer case vacuum switch??
thanks again for your help!

thanks for the info!!
but we just changed the vacuum under the batery and it wasn't that.
but were can i find the front diff actuator and the transfer case vacuum switch??
thanks again for your help!



front diff actuator is under the battery.

t-case switch is located drivers side on the top. Has 3 vacuum hoses coming out of it.

Is there vacuum at the actuator when you engage the 4x4 system?



Also, see if the cable from the from diff actuator is working properly.
Do this by jacking up the front right tire. It should spin freely in 2wd. Have a friend pull on the cable, the tire should not spin if the cable is working.

Procedure

1st Check vac actuator under battery tray for tears, or leaks, and that the vac hose is connected. Replace if found

2nd Check vac hose leading from vac actuator to vac switch on transfer case for cracks and dry rot. Replace if found.

3rd Check remaining 2 hoses from vac switch on transfer case for dryrot or cracks Replace if found.

If all of the above are fine, disconnect your negative battery cable for 1/2 hour then reconnect it. If your 4x4 works after that you probably have a failing TCCM (Transfer case control module)

If that doesn't solve it, it's most likely the encoder motor.

The "transfer case switch" is a mis-named part because it is actually a valve, even though it is commonly called a vacuum switch. It is a mechanically operated valve that is actuated by the transfer case shifter, and will direct vacuum to the front differential vacuum actuator. This valve ("switch") can fail or stick open or closed.
If it fails open, the vacuum is always present on the front diff actuator. This will keep the front diff engaged even in 2WD, causing a whining sound up front, especially loud while decelerating.
If it fails closed the vacuum will never reach the actuator, so the front wheels do not engage.
It is confusing to those who know that a closed "switch" allows flow of electricity, while a closed "valve" blocks the flow.
There really is a vacuum switch in the system, but it is Tee'd into the vac line near front acuator to let the computer know the vac is present there.
If front wheels do not engage here is a simple test you can do. Near the vac ball, pull off the vac hose that goes to transfer case and leave it lay. Connect a 6 ft long vac hose to where you removed the hose. Pull off the vac hose that goes to front actuator and connect this new hose there. This will supply continuous vacuum to actuator so front wheels should be engaged until you remove this test hose. If not then move on to check the actuator and pull-cable. If front wheels are engaged, then you should check the tranfer case switch.

thanks for the info!!
but we just changed the vacuum under the batery and it wasn't that.
but were can i find the front diff actuator and the transfer case vacuum switch??
thanks again for your help!

There is more to vacuum hoses than just the one under the battery. You need to trace that hose back, and all hoses that T in various directions, back to the upper plenum. Even on over to the Cruise, should your vehicle actually have vacuum controlled cruise control.

T
If it fails open, the vacuum is always present on the front diff actuator. This will keep the front diff engaged even in 2WD, causing a whining sound up front, especially loud while decelerating.
If it fails closed the vacuum will never reach the actuator, so the front wheels do not engage.
It is confusing to those who know that a closed "switch" allows flow of electricity, while a closed "valve" blocks the flow.



I think you have it backwards, because a closed valve does blocks flow. So if it fails to open, there will be no vacuum to the actuator.

When 4x4 is engaged, the transfer case shifter opens the valve to allow vacuum to the actuator.

I think you have it backwards, because a closed valve does blocks flow. So if it fails to open, there will be no vacuum to the actuator. When 4x4 is engaged, the transfer case shifter opens the valve to allow vacuum to the actuator.
You have essentially restated exactly what I wrote, except you substituted "fails to open" for "fails closed" which means exactly the same thing.
Please Read it again, I have it written correctly. If a valve is open it allows flow, if a valve is closed it blocks flow.

Mr. Obvious says: "failed closed" means it has failed(not working) and it is closed(even when it should be open)
"failed open" means it has failed (not working), and it is open (even when it shouild be closed).

thanks everybody and i'll try all of that but a nother little question i have a thing that looks like a ball under my hood is that something to do with the 4x4???
and a nother fast question my abs light is on what can it be?? and the check engine light is on too???

The ball is the "vacuum ball" or "vacuum reservoir". Simple explanation= it stores vacuum.

Mr. Obvious says: the ABS light means to check your AntlockBrakingSystem. The Check Engine light means you have to read the codes to see what's up. Autozone will check it for free.

so it does have something to do with the 4x4??
thanks

You have essentially restated exactly what I wrote, except you substituted "fails to open" for "fails closed" which means exactly the same thing.
Please Read it again, I have it written correctly. If a valve is open it allows flow, if a valve is closed it blocks flow.

Mr. Obvious says: "failed closed" means it has failed(not working) and it is closed(even when it should be open)
"failed open" means it has failed (not working), and it is open (even when it shouild be closed).



HAhahahah!! You are right. I was reading a "to" into it as in "fails to open".


Shit happens...

Just a quick question about the vacuum for the 4x4....

What size vacuum hose to the transfer case switch and then up to the actuator??? It's cold here in CT. and I'm too lazy to go look right now...I want to pick some up at the parts store...
Thanks guys...
and BTW, this forum was GREAT for troubleshooting the 4x4.

Steve

What size vacuum hose to the transfer case switch and then up to the actuator???

5/32"

Thanks...:)