Chevy 4x4 not working.

Bushleague · #1 03-16-2019, 08:56 PM

I took the family ice fishing today, and found out the hard way that the 4x4 on my 2004 Chevy crapped out at some point in the last week. In 4hi and 4lo I have no power to the front wheels, in both 2 and 4 wheel drive I can hear a clattering sound when I drive at low speeds. The sound seems to be louder if I'm listening out the passenger window, and seems more to be coming from the diff, and not the t-case, though this is just a general impression. I'm not super familiar with the workings but I did some minor trouble shooting on the lake and though I'd pass along what I found in the hopes someone else can point me in the right direction.

With the truck in park and in 2 wheel drive I can turn the front drive shaft, with it in 4x4 and in park I cant... so to me that indicates that my transfer case is working properly, as well as the electronics in the cab. The drive axles seem fine, so I don't think the clattering is not coming from the CV joints, though it sounds similar to a bad CV joint. Tomorrow I'm going to jack up the front and see if I can further trace the clattering sound by spinning the wheels by hand, but I could sure use any good advice I can get. At this point I'm sort of leaning towards the actuator on the diff, and wondering if its possible that something broke off and is rattling around in the front diff, is this even possible? Thanks.

bubba 96 · #2 03-16-2019, 09:09 PM

Probably have a leaky vacuum line, not engageing them, very common problem. Or the solenoid..

MountainTi · #3 03-16-2019, 09:16 PM

Chev still use the actuator in the front diff? Believe it was electric at one time and failed occasionally

Bushleague · #4 03-16-2019, 09:25 PM

Quote:

Originally Posted by MountainTi

Chev still use the actuator in the front diff? Believe it was electric at one time and failed occasionally

See, that's where I'm not super clear. I'm not exactly sure what portion of the 4x4 system is not in use when its in 2 wheel drive on a 2004 Chev. My experiment with the front drive shaft would indicate that anything past the t-case is not used, but I can see an electrically operated actuator looking thing on the front diff though.

None of which explains the clattering sound. I listened to it over and over again at various speeds and on different road surfaces, and it very much does not seem to be an unrelated noise from the suspension. To me it seems to be somewhere in the drive train, but if the t-case isn't spinning the front drive shaft in 2 wheel drive then it cant be u- joints. And since the drive axles look good it seems like it would have to be the diff itself... though I really, really hope someone can tell me otherwise.

MountainTi · #5 03-16-2019, 09:30 PM

Last chev I owned was a '93, so been a while. Actuator may not be stroking enough to fully engage? Pull the actuator and see if it is. I do remember changing a couple of them, but again, that was a long time ago

overhere · #6 03-16-2019, 10:33 PM

Sounds like you blew up a CV shaft . Jack up front end and put in 4x4 see if you can turn the tires. Also will see if the diff is or isn't locked at same time . If you rotate one tire. Other will spin opposite way if locked in 4x4. There is a chance the lock ring in front diff is broken have also seen that .

cdmc · #7 03-16-2019, 10:39 PM

No vacum lines on gmt800 series truck 4x system.
If the tcase is actuating properly from the cab then the electronic front diff actuator, diff issues. Drop the oil in the diff, check for shineys.

Bushleague · #8 03-16-2019, 11:35 PM

Quote:

Originally Posted by overhere

Sounds like you blew up a CV shaft . Jack up front end and put in 4x4 see if you can turn the tires. Also will see if the diff is or isn't locked at same time . If you rotate one tire. Other will spin opposite way if locked in 4x4. There is a chance the lock ring in front diff is broken have also seen that .

OK, so if the front tires spinning in opposite direction thing is happening, does that mean that my actuator is working? Tomorrow I will jack the front up and have a better go at it, but from my preliminary twiddling and shaking of things I do believe that the diff is locking up in 4x4... but all the CV boots I could see were in good shape. Seems like if a cv joint was blown I would have twisted and or torn the boot... but once again, I'd be pretty happy to be educated on the matter if I'm wrong.

Opalsasquatch · #9 03-16-2019, 11:38 PM

There is a sliding collar that locks the pass axle to the front diff, electrically operated

The actuator could be non functional, or the collar can break.

The front driveshaft is operating normally

Pm me tomorrow if you need a hand

eric2381 · #10 03-17-2019, 07:13 AM

I bet it's the actuator. Same thing happened to my 2002 last summer

overhere · #11 03-17-2019, 07:59 AM

Pm sent

Savage Bacon · #12 03-17-2019, 08:44 AM

Aluminum engagement fork has a guide nub that breaks off and doesn't let the front axle engage. Truck thinks it's in 4x4 but it isn't. Get the updated design

Bushleague · #13 03-17-2019, 11:32 AM

Allright, thanks everyone for the help. I got the front end jacked up and started spinning things and it became pretty obvious that I blew a CV joint, my little world is now back as it should be

. I suppose I should have done that first before getting worried about the diff, but every time I've had to do a drive axle the CV boot is all tore up, and to my half informed logic it seemed like I should still be getting power to one of my front wheels if a CV joint went.

Anyways, thanks to everyone, especially those who PM'd me some very solid advice. Should have the old girl back on the lake for next weekend

Savage Bacon · #14 03-17-2019, 12:34 PM

Good to hear!!

Big_Willy · #15 03-17-2019, 12:47 PM

I owned a 2002 Chev Avalanche. 4WD system would be the same as a Silverado or Sierra.

At about 200,000 kilometers the truck stopped shifting into 4WD, that is, I only had 2WD.

Took it into the shop and tech diagnosed a bad 4WD module. This module is behind the dash board close to the 4WD selector switch. Found a used one at a wrecker for $75.

While the truck was on the hoist, I had the tech replace the encoder motor which is usually the source of 4WD problems.

Problem solved. Total bill was about $400...

-Willy

Bigwoodsman · #16 03-17-2019, 03:40 PM

Quote:

Originally Posted by MountainTi

Chev still use the actuator in the front diff? Believe it was electric at one time and failed occasionally

This. Has happened to me as well. Easy fix if you’re mechanically inclined.

BW