99 Blazer LT cannot disengage 4WD Lo

[shaun88]

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

[chcknugget]

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.

[BlazerLT]

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

[shaun88]

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.

[BlazerLT]

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

[shaun88]

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

[shaun88]

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

[BlazerLT]

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.

[chcknugget]

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?

[shaun88]

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

[Mikado14]

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.

[shaun88]

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.

[shaun88]

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

[Mikado14]

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.

[shaun88]

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