99 4.3L 4x4

sup...

got a '99 blazer 4.3L with teh auto 4x4, 4hi, 4lo pushbutton transfer.

keeps throwing "service 4x4" light... sometimes resolved by the time i start again, sometimes resolved just by turning the ignition off and on again. when it throws the service light, the transfer selector switch briefly "blinks" (once) very quickly then all lights go out.

i'm also hearing a pretty significant "whine" (such as a tranny in reverse) coming from either the tranny or xfercase, noticeable at slow speeds (less than 30mph) but in general a LOT of drivetrain noise. all drivetrain fluids were changed about 500 miles ago when i had the sunshell replaced. i'm hoping the tranny service didn't trigger this.

any ideas? fuses are OK.

Pull the upper plug and see what comes out. You should see a blue fluid. If it's red, or worse yet, black as tar - drain, flush it and refill with GM Autotrak-II fluid. 3 quarts should do you, and only the GM parts counter has it. It may have been refilled with Dextron-III by mistake... Good luck.

Check the vacuum line going to the transfer case actuator.

ok when the service light is on, 4x4 is stuck engaged.

conveniently, the alternator also died, but i got that handled (or will tmorrow that is)


i removed the battery and tray, the vacuum switch doesn't move when the car is turned on, but it en/disengages freely when manually operated, and i can hear air squishing from the sensor/switch/whatever that is on the firewall right up above and center.

from there i see it tapping into another vacuum line and from there i can't trace it.

i looked around the xfercase, i dont see any vaccuum lines 'cept a suspicious one that attaches on the top out of reach.

where should i be checking exactly? w/o a vacuum schematic i'm kind of lost.

I just have to say it, LT .... you seem cool but you must be in love with your vaccum :rofl: Everytime someone has a problem you say "check the vaccum" and occasionally you tell them to clean something. I'm not trying to be mean or say its bad advice its just funny. I'm sure you know about 10 times more about Blazers than me.

I have a simular problem...
I too have a 99 blazer LS 4x4 that I recently bought. When I try to go into 4hi or 4lo the lights in the cab say it's in, their is the clicking noise under the car, however I am still in 2hi. Only one wheel spins in the dirt. I checked the vacume actuator at it seems to be working ok. Any suggestions?

I just have to say it, LT .... you seem cool but you must be in love with your vaccum :rofl: Everytime someone has a problem you say "check the vaccum" and occasionally you tell them to clean something. I'm not trying to be mean or say its bad advice its just funny. I'm sure you know about 10 times more about Blazers than me.

hEHEHE....

But, I am usually right.

I have a simular problem...
I too have a 99 blazer LS 4x4 that I recently bought. When I try to go into 4hi or 4lo the lights in the cab say it's in, their is the clicking noise under the car, however I am still in 2hi. Only one wheel spins in the dirt. I checked the vacume actuator at it seems to be working ok. Any suggestions?

Seems to be ok?

How do you know, did you remove it? Did you check the tubing for a vacuum leak?

this morning I pulled it out, checked the vacum going to it. (constant vacum no matter what drive I am in [2hi, 4hi, 4lo] however vacum increases as you go from 2hi to 4hi to 4lo. Vacum caused the actuator to pull on the cable that goes under the car. I just found it strange that my lights in the car are working but he 4wd isn't I haven't come across anyone w/exact problem yet. Also does the vacum actuator have anything to do with the rear wheels locking in. Like I said earlier only one wheel spins in 4hi or 4lo. Should they not both spin?

just out of curiosity,

should the front driveshaft turn at all times?

i had always figured with the front diff unlocked (not in 4x4) and the transfercase in 2hi, the front axle would sit idle.

i noticed today that the light wasn't on, the car shifts fine from 2hi to 4hi and 4lo, but in EVERY gear the front axle spins (such as rolling the car in neutral).

is that right or is my xfercase stuck in 4x4?

You have to see if the front vacuum switch is actually doing its job.

Also, the front shaft turn all the time.

So BlazerLT you are saying that if the truck is jacked up front and back should all the wheels be turning in 2w hi or just the back? Also the vacume switch on top of the transfer case that is hard to get to does that just pull apart like a plug or what? I put a light up and still can't see how it is connected I can barely get my hand up there but it is very loose and I wanted to unplug and check it. I am having my 4wd problem again and still playing with it.

Thanks

Just the back. The front driveshafts essentially freewheel until you start the 4x4 and the transfer case put power to them.