First winter with this 2000 S10 FWD. Big snow storm yesterday and trying to get up the street 1/2 block from home in 4WD. Then 'pop' I can't go any more. Indicators say I'm in 4WD but only back tires spinning. Retry engaging from 2WD to both 4WD HI and LO with indicator lights. Worked for just few seconds then 'pop' and back to just rear tires spinning again. Made it back to my driveway luckily without 4WD. Don't know a lot of how this 4WD works but understand it works with vacuum and diaphragms under my battery somewhere. Is this the colporate? I sure miss the days when you engaged the lockouts and could just mechanically put a 4WD vehicle into 4WD HI or LO and not worry about whether you have 4WD or not. These dependencies on other vehicle functions is not a step forward for convenience or otherwise.

 

that sounds like a front axle not locking properly. There is an article on the front axle mechanism in the tech help/self help section (front axle clicking). Please read that and come back with any questions. Yes I know it's not your exact problem but the info is still very useful.

 

Thanks for the reply and advice. I'll search for that and read up on it next chance I get. Hopefully I'll learn something.

 

Which 4wd system do you have? 3 or 4 button? I recently had a vacuum leak detected in my actuator valve, which is mounted at just about the center of the firewall (4-button 4wd system). I've read the vacuum actuators mounted to the transfer case (3-button system) fail fairly often.

 

Thank you for your reply. I have the three button 4WD. From what I've read so far on this site I believe that my front axles are disengaging from either bad lines or possibly a bad diaphragm. The conditions were about 8 inches of snow and brutally cold (below zero). This is my first winter with this truck and have driven it before in much lighter snow and higher temperatures without any issues. I am concerned as to find out why the front axles were engaged and then disengaged on it's own. I was able to re-engage the front axles once more but only for a few seconds and that was it. Seems if it were bad lines or diaphragm then I shouldn't have been able to engage my front axles at all. Is it possible to have enough vacuum to initially engage my front axles and then have the vacuum bleed off somewhere along the line? Could this vacuum actuator that you mentioned still be the problem? I still haven't been able to dig into the problem yet due to the weather. Hopefully it'll warm up a bit later this week.

 

Could it be the axle locking mechanism was stiff from the cold and not fully engaging (giving the pop when it slipped back out)? Few things more frustrating than a 4WD system that works when you don't need it and doesn't work when you do need it!!!

 

Doubt that this is a vacuum problem, sounds more like the collar/gear that the vacuum actuator moves that engages the front axle is not fully engaging...so it pops out. Could be that the cable that the actuator pulls has some water in it, which becomes ice, so not able to fully engage the collar/gear.
Pretty easy to check, but requires getting under the front with the shield remove to "have a look see".....

But could be far worse in that the collar/gear is chewed-up and requires replacement.

Also need to check that the transfer case encoder motor is also moving to put power to the front. Could be snow/ice is packed around it. Again...have to get under to "have a look see".....

Know anyone with a garage you could use for an hour?

Good luck.

 

Yeah that is most frustrating. I don't know exactly where the problem lies yet as I have not had time to physically dig into it yet. I'm guess I'm hoping it's not a deep mechanical issue.

 

Thanks for your reply. I'm assuming the transfer case is working properly as I'm getting the light indicators that say I'm in 4WD HI, LO and 2WD. And I do agree with you that I feel the collar/gear is not fully engaged. But I guess I'm hoping that it's a vacuum/diaphragm/cable problem vs an internal worn collar/gear problem. I'm still educating myself on what the transfer case encoder does exactly and if this is something to be concerned with. The 'pop' I refer to is just like you would feel if while under load you bumped or accidently popped your manual tranny out of gear without using the clutch. In my case I'm assuming it's the front axles suddenly popping out of engagement. I don't know if ice or snowpack have anything to do with it but have my doubts as I had not driven in any conditions to really support that other than the day this happened and I only got 1/2 block up the street. But that's not to say that couldn't be the problem. I do have an unheated small narrow one stall garage. Finding the time and right weather conditions holding me back from digging into it just yet.

 

I agree that is sounds like the transfer case and encoder motor are working correctly.
Like I mentioned above, the actuator under the battery pulls a cable that actually moves the collar/gear to engage the front axle; if the cable gets stuck due to rust or something, then the collar/gear is not fully engaged and is popping-out when under load.
Suggestion is to pull the cable using pliers, note travel, then compare this to how far the cable is pulled by the actuator......or just pull the cable and use locking pliers to keep the cable in that position, then see if it stays in 4wd.
Just be sure to do this on gravel/sand/...not pavement as driving on pavement in 4wd will destroy the CV joints....will...that is what I have been told due to the front/rear axles not in full synch.

Could be as simple as drops of oil into the cable.

Let us know what you find.....when weather permits.
Only going to be 72°F here today.