Front axle 4x4 engaged. 4x4 not selected.

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04-22-2018, 04:01 PM

packrat1969

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Front axle 4x4 engaged. 4x4 not selected.

Can someone point me in the right direction to determine what position the front axle 4-wheel drive actuator should be in for 4x4 and 4x2 operation? I don’t have four-wheel-drive selected, but the front axle appears to be engaged. When does the actuator draw in the pushrod/cable (towards itself)? 4x4 or 2x4?

I’ve looked at the actuator, under the battery, and it seems to move the pushrod/cable easily. What kind of throw should I expect for movement on this thing? Half an inch? An inch? The vacuum tubing looks like it’s in good shape, and I can draw the actuator in by applying a vacuum to it. Is it common for the pushrod/cable to break?

packrat

04-23-2018, 05:24 AM

Transman304

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Vacuum switch on transfer case is stuck and needs replaced.
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04-23-2018, 09:43 AM

LesMyer

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Quote:

Originally Posted by packrat1969

You need to go back to your other thread on this subject and follow through.

https://blazerforum.com/forum/steeri...ll-time-95890/

Transman, from the other thread he has a NP8 - so no switch on the transfer case.

Last edited by LesMyer; 04-23-2018 at 09:46 AM.

04-23-2018, 10:36 AM

Transman304

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Thanks Les, with no vehicle information I was guessing at the most common problems.

04-23-2018, 03:08 PM

LesMyer

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Quote:

Originally Posted by Transman304

Thanks Les, with no vehicle information I was guessing at the most common problems.

Yep, I also thought it was probably the vacuum switch and told him how to check. Just a different switch (and electronic) for the NP8 as you know. Interesting thing is if you get the two hoses switched on the NP8 electronic switch, it will not exhaust the vacuum and disengage the front axle when the 4WD is turned off. I had this happen on mine. Just thought it was a bit irritating for the OP to abandon the first thread, apparently without following intructions, and start a new one with pretty much identical questions. You can lead a horse to water.........

Last edited by LesMyer; 04-23-2018 at 03:12 PM.

04-23-2018, 03:23 PM

packrat1969

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I apologize for not following up with the other thread, but I couldn’t remember which S10 Blazer site on which I had posted it. I was also standing right in front of the car at that moment, and on impulse I decided use my iPhone, instead of going in the house and firing up the PC. For some reason, the search function had failed to produce any relevant results. There does appear to be an electrically-controlled vacuum valve just upstream from the actuator. I’ll give that a test the next time I get back to the vehicle.

Thanks for the help

packrat

04-24-2018, 07:38 AM

LesMyer

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First check to make sure front axle is still locked while in 2WD (malfunctioning) by starting the engine, jacking up the right front wheel (only), and seeing if you can easily turn the tire. If you can turn it without extreme effort, axle is not locked in and you don't have a problem. If you can't turn it, then disconnect the hose coming from the solenoid on the firewall and see if it releases. If it doesn't release look at the bellows/cable or axle locking mechanicals. If axle does release with hose disconnected, you might be trapping vacuum so switch the hose positions on the solenoid and try again. If still malfunctioning, check solenoid operation (does it shut off during 2WD). Don't forget to keep vehicle running during all of this, and to make sure that light is on steady in the 2WD button. Do things in the stated order. Good luck.