I bought a 2002 Suburban Z71 last week with 167,000 miles. It's super clean and everything works, uh except the 4 wheel drive. I didn't find that out until today when we got a decent snow. I'm pretty upset because the seller assured me it worked and I didn't have anywhere to really test it by his house. So I bought a 2wd at a 4wd price.


The 4 hi, 4 low, 2 hi and auto 4 will all light up when pushed. I can hear a small click inside the cab and another actuator type noise (?) by the transfer case. All indications are that it's in 4 wheel drive, but the front wheels do not spin. It's 10 degrees and snowing out, so I can't really check anything out today. I did check the 4x4 fuse on the driver's side dash. It was good, but I replaced it anyway.


From what I have researched it could be the actuator, encoder, clutch pack or bad air line. Anything else it could be?


I'm not a mechanic so I don't even know where these parts are. As you can imagine, I'm stressing out wondering how much this is going to cost. I could really use some advise. Where do I start and how do I check?

 

Is it possible that it's not engaging because it's so cold?

 

Welcome to the forum.

If it's the cold, then something is wrong.

FWIW, you can check 4WD by engaging it and driving in figure 8s on dry pavement like a parking lot. It's working if you feel the wheels hopping as the outer and inner ones slip while trying to rotate at the same speed.

 

Thanks for chiming in and the welcome 73 Shark! I'm familiar with how 4wd works. I mostly assumed it worked in the Suburban because it was in such good condition. The prior owner lived in a congested area and I was a long way from home. I should have been more thorough. Nobody's fault but my own.








I took it out again and transferred it from 2wd to 4wd and forward to reverse a hundred times and the front wheels still won't pull. I was hoping I could free something up by cycling it over and over. I don't believe it's from the cold. I texted the prior owner and asked if he had problems with it and he said he only used the 4wd maybe five times, but it always worked for him.
Low range works fine, but only the rear wheels spin in it also.

 

From what I have gathered by reading forums all night, I probably have a bad actuator. Watched a youtube video and it seems pretty straight forward to replace. Unfortunately, I won't be able to replace it until the snow is gone.


Any other ideas are very much appreciated.

 

Given that most who buy a 4WD (new) don't really need one, or, maintain it. Most of the problems one has when buying a used 4W is because of non use and that lack of maintenance.

If a 4WD isn't used or the Fluids changed, it has a tendency to "goop" up, and doesn't want to change when you need it. If you haven't changed out the Fluids in your Differentials and Transfer Case, that would be my first suggestion toward a fix, then...

With the new fluids, even then the apparatus needs a little help in making the change. Often times, if you get going about 5mph, shift it into neutral, then press the 4HI button, the rotation of the gears and shafts with no pressure on them, often allows things to slide into place. You may have to speed back up and try this several times, before a shift will occur.

You can try this "rolling" shift between 2WD an 4HI, then between 4HI and 4LO. Treat these two separately, but you must be in 4HI before you can access 4LO.

If and once you do get a change to occur, don't stop there !
Change it back and forth several times, to get things unstuck, and, go through the changes 2WD-4LO about once a month, to keep things working.

 

most common issues are with either the switch, encoder motor or front diff actuator.
Shift into 4wd hi, does the 4wd button led light up and stay on


if yes, have someone watch the front drive shaft as you drive by; is the front drive shaft turning. if yes, you can rule out the shift button an encoder motor. the problem is most likely in the front diff actuator.
if the front driveshaft is not turning, check for power and grd to the encoder motor.
if that's ok, shift to 2wd, remove the encoder motor and connector, place a wrench on the tcase shift shaft and manually shift into 4wd. if the truck front drive shaft now turns...you need an encoder motor.

 

You guys are awesome! Thank you so much! Makes me feel much better knowing it's probably something simple. I'll report back when I figure it out. Thanks again!!!

 

Update:


I've been trying to engage the 4x4 ever since and still no luck. Today I removed the actuator and pushed the 4 hi button. The actuator worked. It moves in an out. I sprayed it clean and reinstalled it. Still no pulling from the front wheels.


I had someone watch the driveshaft and it was turning.


I have not changed the fluid in the differential! Is that the next step? Is there anything else it could be?


I don't believe anything is broken internally because I prior owner said he rarely used it. The indicator lights stay on and don't blink. No message comes up either. It seems to me that the computer believes the front wheels are pulling.


I really need this fixed. We got a foot of snow a few days ago.

 

Bump! Would changing the fluid help anything? Any other ideas?