s10 4x4 trouble

[herby31]

so anyone who can help point me in the right direction on this gets my undying gratitude. and maybe some bacon. my truck is a 2002 s10 pickup, 4x4, with the 4.3L v6 and an automatic transmission and electronically controlled transfer case and factory optioned lockers front and rear. as far as i know, everything is still stock. (i bought it used.) it has not been lifted, and the tires are oem sized. i got stuck in some mud recently, and my buddy that pulled me out pointed out that my front tires weren't driving. i put it up on jackstands on the frame, started it, and shifted into every setting on the tcase. 2 hi works just fine, 4 hi drives the rear tires and front drive shaft, and 4 lo drives and locks the rear and turns the front driveshaft. so what is wrong with my front differential? there is a cable that runs into the front differential and then up towards the right front corner of the truck. does this cable serve to mate the differential to the spinning driveshaft in some way? has anyone had this trouble before? i'm really hoping to get this solved soon. its sucks to get the lower fuel economy from having a 4x4 without the extra capabilities of a 4x4. please send your wisdom my way, and i swear i'll be your bestest buddy forever.

 

[jnicol6600]

there should be an eletronic actuator in the front differential that engages the gears for the front. Its pretty easy to change on the older trucks. should have a couple of wires going to it. The cable you saw was probably a vent tube.

 

[jclark]

there should be an eletronic actuator in the front differential that engages the gears for the front. Its pretty easy to change on the older trucks. should have a couple of wires going to it. The cable you saw was probably a vent tube.

Yup.

 

[remymartin]

+1 on the actuator in the front diff.. Very common.

 

[rich8483]

is this "actuator" an electric hub? my dad's '00 f250 has a similar situation, but if you get out and manually lock the drivers side hub, (which it should do electronically) it works fine.

 

[jnicol6600]

is this "actuator" an electric hub? my dad's '00 f250 has a similar situation, but if you get out and manually lock the drivers side hub, (which it should do electronically) it works fine.





no not really. I think they just unhook one axle from the differential. but in the hogshead not at the wheel. that way it doesnt spin the driveshaft. Makes me wonder about the front locker thing. I dont even think they are available for the IFS bowties. Dont flame me if they are I havent messed with one for a while.

 

[sgt.porter]

I've never had a vehicle with an electronic actuator, but chevy's tend to have a problem with not locking the hubs if they get dirt in them. if the actuator isn't the problem, pull the hubs, clean them then grease and reassemble them. had to do that every couple years on my old truck to keep the 4wd working right.

 

[herby31]

thanks for all the input, folks. i will try some of these ideas and let you all who was right.

 

[Mr. Habib]

Is this electronic actuator like the old vacuum disconnect in the front axles of older Jeeps?

 

[Aaron B.]

Not your year and options, but may help you:

On 1996 model S-10's w/ manual T-case, the actuator is a vacuum actuator located toward the front of the engine bay, accessible from under the hood. If the front axles aren't engaging, it usually means you have a bad actuator, or a vacuum leak going to the actuator. You can see the actuator stroke and pull on the cable if it is functioning correctly.

No idea what they changed between 1996 and 2002, maybe the other guys are right and it was changed to electronic. Perhaps someone will chime in if there was a known change.

 

[jfed85]

Had a 99 Jimmy and my front drive quit. In my case it was the actuator. Definitely check into that.

 

[T-rav]

Im not good at online diag, but since Im in Ft wayne Pm me with your number and maybe I can come help out.

 

[BURNSURVIVOR725]

+1 on the actuator. if i remember right its around $100

 

[eldirector]

I had one of these trucks. The vacuum actuators sucked (actually, not sucking was the problem).
Chevrolet Blazer 4x4 Transfer Case Motor 4WD Actuator Switch At Monster Auto Parts

Scroll towards to bottom. They are pretty cheap. Check the vacuum lines first, and then the actuator.

Here are a BUNCH of links to forum posts on the same issue. Might help with troubleshooting:
s10 cable actuator - Google Search

You can also replace the crappy vacuum system with a manual cable system. You might be able to rig something up yourself, or just buy it (below). With this, you engage the 4x4 shifter, and then pull the manual cable.
Posi-Lok Replace your failing factory vacuum shift motor to front differential - Drivetrain.com

Good luck

 

[cbop]

The way that system works is that there is a vacuum switch on the transfer case that is actuated by a cammed ramp inside the transfer case. This vac switch is located over the front output shaft of the the transfer case (the front driveshaft). There are 3 vacuum lines to this switch, one is engine vacuum, the 2nd line is a vent that goes up to a small foam filter, usually buried somewhere back by distributor which allows the system to release the vacuum where shifted back into 2wd and the 3rd line goes to a vacuum servo, mounted low in the front of the right front fender. I can't remember if the battery is on that side in that year but if it is, the servo is below the battery tray.

When you shift into 4hi or 4lo, the cam inside that transfer case moves a small, spring loaded ball in the vacuum switch, allowing vacuum to pass to the vacuum servo which pulls a cable that is attached to a fork in the front differential, engaging the front drive.

The things that go wrong with this system, in order of frequency that I have seen is:
The ball in the vacuum switch sticks and prevents the vacuum to go where it suppose to. I have replaced so many of these over the years, I could not even begin to guess how many.
second most common is a vacuum leak to the switch, either due to a general vac leak or the hose melting against the exhaust.
Third would have to be a rusted cable from the servo to actuator and the last being the servo itself.

The easiest way to check this system is to take the vacuum connector off of the switch (note that there is a little 'peg' for correct orientation of this connector but I have seen some determined people get it on wrong never the less). With the engine running, in park, check for vacuum on one of the ports, if not, trace the hose back to the problem. If there is vacuum, shut the truck off and take the switch out to see if it is stuck. Having never seen one before, you likely won't be able to tell if the ball is stuck so you may have to take it to the parts department and compare it to a new one.

If you haven't found the problem yet, you will need to access the servo which generally requires removing the battery and tray but I would guess that I only have had to do that on very few. 75% are fixed with a vac switch, 20% on vacuum leak and the remaining 5% would be cable, servo or front axle problems.

Good luck

 

[herby31]

thanks everyone, for the help. el director and cbop, your advice lead me to the problem. i had 2 burned spots in the vaccuum line from the tcase to the diaphragm looking switch thingy under my battery. i cut out the bad parts and spliced and re-routed (ziptied away from exhaust) now my 4x4 works like a champ. thanks again, herby.

 

[downzero]

I've never had a vehicle with an electronic actuator, but chevy's tend to have a problem with not locking the hubs if they get dirt in them. if the actuator isn't the problem, pull the hubs, clean them then grease and reassemble them. had to do that every couple years on my old truck to keep the 4wd working right.

The axle on this truck is splined into the hub bearing. There are no "locking" hubs on an S-10.

 

[stephen87]

Too bad I didn't find this thread before. I realize it's a shameless plug but try S10Forum for any future problems. Someone over there has run across the problem before and would be willing help you figure it out. Someone actually had this exact problem with their 4x4 last year and I solutions were very quick to come up.