Bodaggit

Alright. It's a hard problem to describe over the net, but I'll try.

When traveling on a highway I get this noise coming from the front right area of my blazer. Kind of like it's trying to engage the front axle for some odd reason.

It happens mostly after climbing a hill, then letting up as I crest the top of it. So it leads me to believe that is some sort of vacuum problem. Like it is creating a vacuum as it gets a pretty good load put on the engine, or losing a vacuum. I can force the problem to happen too, by purposefully starting up a hill in too high of a gear. When it gets down to that point where I HAVE to gear down, soon as I push the clutch in it starts with the noise again. Still vacuum I think.

So, I start off by changing the vacuum switch on the transfer case. Didn't fix it.

Then I move to the actuator under the battery, change that.... still no good.

The cable from the actuator to the front differential moves freely, very easy to move back and forth.

I guess I am just kind of at a loss of where to look. Would some sort of odd vacuum problem cause this? I can't see how a leak anywhere would be trying to engage the front axle, more likely it would keep if from engaging I would think.

Right now, this is my one and only vehicle. Can I just unhook the vacuum line from the actuator and keep it from trying to engage the front axle? As far as I know that is the only thing that would cause it to engage. Also, I would probably go ahead and remove the front driveshaft as well. That is, if it would help me at all to drive it for a couple of days while I trace down the true source of what is causing this.

So, will unhooking th vacuum from the actuator be worth trying? Anyone have any idea of what else is going on? I need help with this thing since it is my only means of transportation. Already being able to rule out the vacuum switch on the transfer case, actuator, and cable should be of some help.

OverBoardProject

There's a vaccum switch located somewhere on the T-case, and it almost sounds like the switch is leaking slowely to me

muddog321

Depends on what year so if 98up see FAQ section - no vac switch on xfer on them - looks like yours is 2001 from profile - there is an electric solenoid/vac switch on the firewall - follow the lines and with the engine running and in 2wd the vac should not be passed thru so pull the line on the out side (to vac actuator) and if its got vac switch is bad (and you should hear the axle coupler unlock too).

agcneo

ya im having a similar problem, mines a 97. mine was acting up on my way home one day, but instead of trying to engage, it mannaged to almost fully engage, locked my front end and sent me off the road. blazer lt is helping me with this one. so far i took the fuse out after tryin to enage it for a lil bit, and when i heard no nose, i pulled the fuse. hasnt acted up since. not sure if that provides you with a temporary fix or not. hopefully that helps untill you can find the permanite cure.

__________________
you may have a faster car.....but i can still drive over yours

Bodaggit

You sure about the no vac switch on them? I switched one out on mine already. It may not be technically called a switch. Here is a link to what I put on it. http://www.partsamerica.com/ProductD...pe=863&ptset=A

I replaced that "switch" on the transfer case. I also changed the actuator under the battery.

I still believe the problem is vacuum related somehow or another. I can't figure how the actuator would be getting vacuum put on it.

The noise doesn't happen all the time either. I could drive flat land all day, and just so long as I didn't put a heavy load on the engine it would never happen. Just when a good load is on the engine, such as going up hill.

I'll check some of the suggestions though, never know what it might be with these types of things.

LS19962DRBLAZER4X4

I had problems with this 4x4 transfer switch since 1998. My 96 LS 2DR S-10
4X4 BLAZER was given me trouble since I owned the truck in early 1996.
Transfer switch vacuum cable, ect. ect. no one seemed to know what
the problem was, all they wanted to do was PAD the bill with their overkill
labor and parts. The GM dealerships never gave me any solutions. I sued
the dealership GM for the parts and service and won.. I never 4wheel drove
the vehicle because I knew it wouldn't be able handle rough driving. I had
the 4x4 serviced in 2001 and it has been okay ever since. It was a private
garage auto service ( he repaired it in 2 hours and it hasn't broken down since). Stay away from the dealerships, they stink...
They sold the truck to me as a 4x4 and when they learned it was they tried
to weasle out of the suit by saying it was a monified 4x4 ? (whatever that
meant)...
I was told by the Lemon Laws of my state that 23000 other Blazer vehicles
sold that year has similar problems and GM placed it in their files and forgot about them...

Bodaggit

I believe that. Out of site out of mind for them. Won't be fixed till it kills someone. Until then it's just an easy way for them to make money fixing them.


Anyway.... I have a quick question. When should there be vacuum to the actuator under the battery? Mine has vacuum in 2wd, but goes off in 4wd. Is that correct? I'm not sure which way is right. I thought it should be the other way around, but I've been wrong many times before.

Bodaggit

So, does anyone have any idea about this?

BlazerLT

You sure it isn't a wheel bearing gone?

__________________
1995 Factory Blazer Service Manual for sale, PM if interested.

muddog321

That xfer case switch is actually a sensor that tells the TCCM (computer ) that the low gear is engaged for 4LO. Same type on the front axle that tells TCCM the axle coupler is engaged for any 4wd mode. Did you pull the vac line at that switch on the firewall yet and test it? That would be my guess - check that front axle sensor too - then disconnect the battery cable for 30 min too for a TCCM reset -yea GM had Bill Gates design this thing (joke).

Bodaggit

No, it's still there, lol. I am positive it isn't a wheel bearing though.

Bodaggit

That's what I was meaning to ask about. I'm confused on when it should and shouldn't have vacuum going to the actuator. It has a vac in 2wd, and no vac in 4-hi, and I didn't check 4-lo. I was thinking it should be the other way around anyway, that there should be no vac in 2wd.

I saw a set up somewhere while doing a search on here that did away with the actuator altogether. It had a pull cable to engage/disengage the axle. You just pushed the 4wd button, then pulled a knob and it was in 4wd then. I've been thinking about that more and more, it does seem more reliable than all these vacuum hoses.

I would almost think the Bill Gates statement really isn't a Joke. I keep waiting for a little LCD screen to pop out of something somewhere on my blazer with the Blue Screen of Death on it.

99church

i have a 99 blazer 4x4, with t-case problems, narrowned it down to the switch that is on the t-case (i purchased the part mentioned above motormite at parts america) but i am can't locate it on my t-case to remove the old, can someone please tell me where it is located. thanks much

BlazerLT

I would seriously not rule it out, when you go over the crest of a hill, you unload the bearing which will change the noise.

__________________
1995 Factory Blazer Service Manual for sale, PM if interested.

Bodaggit

I am positive it's not the wheel bearing. It's not a constant noise like that.

I think I figured out what was happening though.

Something is hooked up wrong somewhere along the line. It had vac going to the actuator in 2wd. When I was going up the hills it was losing just enough vac to start to disengage the actuator. Right now I have the vac line to the actuator unplugged, with a screw stuck in the end of it and taped off. Since then I haven't had a problem with anything trying to engage/disengage.

Now I just need to locate the source of the problem.