4WD issue Chevy S-10
 

1998 Chevy S-10 pickup truck, automatic transmission 200,000 miles, 4.3L V6 with dashboard push button 2WD and 4WD hi/low selector and self locking hubs.

The front wheels are not engaging.

Even 4WD low feels like 2WD, not even the turn radius is affected.

While coasting in 4WD low today it did start to drag with drivetrain friction for a second or two.

I do not know if the front transfer case is low on fluid, or if the automatic transmisson filter is clogged. These are just a couple of ideas which came into my head.

I did have a shop change out the front and rear U-joints in the spring. I don't remember using the 4WD then, don't use 4WD except in winter.

I tossed a couple more 70lb sand tubes in the bed just so I can get around for the next few days. I could operate in 2WD all winter, but it would suck.

Any ideas?

I have worked on GM 4WD vehicles where the front wheels would not engage because the vacuum lines had failed. These were early 2000's vehicles. GMC Jimmy maybe. Post manual engagement at the wheel hub.

Vacuum switch on the front axle I think. Had to change one on mine many moons ago.

my s-10 had a fuse on the switch..you did check the fuse right?

mine went out in tahoe in a blizzard. you find a substitute fuse fast after that.

The vacuum switch mentioned is on the transfer case of a manual shift s-10. Yours has a switch on dash, module in right kick panel, encoder/shift motor on transfer case, vacuum solenoid under hood, and a vacuum servo under the battery to engage the front diff. Hard system to diagnose but if the transfer case will shift to low range then I would suspect the vacuum actuator under battery or its related lines and solenoid. Common for the cable between the actuator and diff to corrode and seize from battery acid leakage. Depending on the grille style I have been able to see the actuator thru the grill and actuate it with a long screwdriver to test operation of the cable. Otherwise the battery and tray must be removed and jumper cables used to start engine to test vacuum supply and operation of actuator.

Thank you everyone for the input.

I now have more than a clue as to where to start, and that is a good thing.

Cheers, George

CHeck the large vacum actuator under the battery.

neither of these idea would come into my mind..

you check the fuse yet?

Scratch that, that may be for the older series trucks.

No but will do that before anything else as it's the least painful under these cold conditions.

I have had my battery leak in the past and suspect it messed up what's underneath.

Maybe my friend with the heated garage which let me paint my truck there will help me out again. Or I could wait until this polar air is gone and just 2WD my way carefully for a while.

you can check the fuse while sitting in the seat if i remember correctly.

i kinda remember a flashing warning light.

Throw 5 or 6 sand bags in the back by the tailgate. That's all I do with my 2wd Ranger and it gets through anything I need in the winter, here in MI. Good tires help the most.

Advanced Auto on Washtenaw/Hewett? will check OBD2 codes for free. Maybe others nearer.
It probably won't help, but it will be what the computer thinks it is.
The guys may have an idea.

I have four 70 lb bags back there now, but I've also lost the weight of the spare tire when it fell off last year.

Couple more bags it is, can always use it on my walk.

When things just start falling off your truck, it should be taken as some kind of warning sign. :D

I might be able to weld the mount back on, George.
On a nice day that is(brrr).