99 Blazer LT cannot disengage 4WD Lo

Hi all

I Have a 1999 Chevy Blazer for some reason i cannot disengage 4WD Lo, when you push the 2WD hi button it flashes for about 5 -10 seconds ,i can hear a relay under the glove box clicking, but nothing happens, it stays in 4wd lo. This question has probably been asked and answered before. Please if anybody knows can they shed some light on this.

Its a right hand drive model if that makes any diff.

Any help would be much appreciated.

Shaun

you have to put your car in neutral @low-to-no mph to shift out of 4low gear. Mine usually disengages after I shift back into gear from neutral. If you try to do it in "drive" it will function exactly how you describe.

^^^What he said, make sure it is in neutral and not moving.

Thanks for the quick reply, have tried with it in park and neutral, have even reversed a few feet to release presure but no luck either, i did read another previous post regarding the sensors on the font diff etc.

Ok, this may seem weird, but pull the negative and positive battery cables from your battery for 15 minutes and try again.

Will give that a go and i'll let ya know how i get on. Thanks

Hi
I took your advice and disconnected the battery, same fault is still there. Tho when I had the battery and box out I noticed the servo underneath was in a pulled in state, so I manually released it.

Now when I start the blazer it still flashes in 4wd lo but its actually in 2wd lo

When I looked around the top of the transmission I noticed a vacuum hose abouit the size of a pen near the loom, it wasn’t going anywhere, maybe this is a breather or should it be going somewhere.
I have read other posts about this same sort of fault and its hard to figure out whats going on.

Hopely something can be sussed out.

Oh if anybody needs any computer technical help don’t hesitate.
Cheers

Ah, that vacuum hose should go to the vacuum actuator on the transfer case and is what is causing you your trouble.

Reattach it and all should be good.

computer technical help! Yes!

My overhead console doesn't work. It displays the temperature for about five seconds, then shows dashes (--). It is the multifunction (mode) console and those functions also turn off after 5 seconds. My compass directions always shows "C". Is this the vss signal not working? How can I test if it is? I installed this factory console into my 96 jimmy and have everything working except for the functions. The 2 wires in question are the vss and serial data wires. Would there be any computer glitches (like "obd1.5' ) that would hinder me?

Sorry i should have been more specific (my fault) for the topic i know but i meant personal computers not auto computers sorry dude

Better check that hose. There are three hoses: Vacuum supply that comes from a T in the area of the distributor, Vacuum line to the front actuator, Vent that goes to the firewall near the heater box side with a vent cap on top. These three hoses are usually bundled together in the transfer case area and terminate into a rubber plug that is keyed to the top of the actuator switch.

You will also find a transfer case vent hose in the same area. Also, and I might be wrong in this case but I believe there is also a vent hose from the top of the tranny.

IMHO, your actuator switch that activates the front axle (the one with three vacuum lines) may be stuck. When you activate the switch to return to 2WD, the front axle is not disengaging and the switch on the front axle is sending a signal that it is engaged, thus the flashing light telling you that there is a problem.

Thats what i thought about the vent hose i will have another look and will check these other hose youk have talked about to. You have mentioned that the actuator might be stuck and the front axle is not disengaging,i have checked it on grass shingle etc its only in 2WD but in low ratio, not even a possible combination that i can see to choose.Plot thickens.

Would there be a way to manually shift to 2WD hi to check to see if 2wd hi is even available? just a thought

The transfer case can be in 2WD and checking the way you said is fine and will show only 2WD. However, just because the front axle is engaged does not mean that you are in 4WD, it just means that the front axle is engaged but the transfer case is not, it is in 2WD. This is a common problem. Real simple to check, if you want, you can remove the actuator located on top of the transfer case, 7/8" wrench. if the ball is stuck into the shaft, that's your problem, if it can move freely in and out, then it's not.

Another way, I think, is to disconnect the electrical plug on the front differential and eliminate the signal.

I will do some work on it tonight and post a reply saying how i got on. Man they sure built these complicated. Thanks for you help.
Shaun

Reconnect that hose.

Last I remember, there is no hangin vac hoses on my 4x4.

Hi again
i had a good look and that hose i mentioned ealier is a breather on top of the auto. If its not to much troulbe could you post a photo of the actuator as i had a good look for it but im not sure what im looking for, only thing near 7/8" was a sensort on the right hand side about 2oclock level on the transfer case.

Also tried the fron axle trick also but didnt make any difference, still stuck in 4wd lo according to lights on dash and driving. (tho front wheels arent driving) also i noticed, when the auto is in neutral with engine running at approx 1500 rpm, the vechile very slowly creaps forward. Any ideas
Cheers

Send me an Email and I will gladly send you a picture of a good one and a bad one. I'm like Fireplug, can't seem to get a picture on this thing.

The switch is on the driver's side, If you follow the front driveshaft back to where it bolts on to the yoke of the Transfer case, it is behind it. It has 3 rubber vacuum hoses.

And don't be hooking that vent hose up to anything, just leave it where you found it.

shaun_sandford@hotmail.com , i left that hose where it was. Thanks man everybody is so helpful here.

Here is the picture, a good one on the left and a bad one on the right. Notice the stuck ball on the bad.
http://files.automotiveforums.com/gallery/watermark.php?file=/500/227753part4wd.JPG

That would be the beast.

Thanks for that Mikado14 will post a update tomorow after i crawl under neath.:-)

Stop, Park, 2WD :-)

Crawled under neath today and i looked everywhere around the front driveshaft and i couldnt find the actuator, only thing i did find was sensor like switches with similar plug on end of it.
If the shifter cable was slightly out of adjustment do you think this could be a problem with shifting 2wd-4wd etc. cheers

In your original post, you mentioned that you removed the battery box and the front axle actuator was engaged. The cause of this is that it is receiving vacuum to cause the actuator to pull back and engage the front axle. You also mentioned that the transfer case was in 2WD and you stated how you checked it. Now, all things being equal here the culprit would more than likely be the vacuum actuator switch on the transfer case. If you look around and find the vacuum hoses, follow them to the driver's side of the transfer case, the switch is on the side that is flat and about 4 inches from the front yoke.

As to the cable being out of adjustment, I doubt it unless something has happened inside of the front differential, then there are other problems.

Are you talking about a Left or Right hand drive model, as mine is Right hand drive. Had a look today and followed your instructions. Only one close (its oposite to what you said tho) is a normal sensor, its all black, two wires, and on the end its like a small contactor. None of the sensors i have taken out have a ball bearing, have taken out 3 in total. One right on top of transfer case closest to body of truck. Another near yoke on passenger side, and other one is on right hand side of transfer case. All of them are the same as described. I might get some pics taken. Also there is only one vacuum hose going to the transfer case which goes is about 4-5 inches away from the yoke. Maybe there are different transfer cases from LHD and RHD. As this blazer was imported from japan.

Guys he said a 1999
If I remember right around 97 the push button system is controled by the TCM . I dont think there is a vacuum switch on the transferrcase. But I could be wrong

Holy can't read the post! Your right Fireplug! Geez, talk about having blinders on. Sorry shaun88, I had you chasing phantoms in the dark. You have electronic issues, get a manual and go through the checks.

Ummm I have a 2000 and mine has a vacuum switch that was replaced........

do you have the floor shift rod your push buttons??Alexxn

I have push buttons on the dash

1999-00 DTS136-1 236GM 27 spline front input, rear slip output male front output spline (electric shift)
There is no vacuum switch on 1999 and up transfer cases

does anyone know how to remove the front drive shaft on a 2004 blazer? I have removed the 4 bolts yet it still will nnot move, i am trying to replace the transfercase motor.

does anyone know how to remove the front drive shaft on a 2004 blazer? I have removed the 4 bolts yet it still will nnot move, i am trying to replace the transfercase motor.

This thread is 5 years old please start a new thread with your question and I'm sure you'll get help.