Front Wheels Don't Spin in 4X4

[seanpooh]

So I was changing out my inner tie rod on the driver side since the alignment tech showed me there was play in the wheel. Come to find out after changing the tie rod, it's actually the wheel hub that has the play holding the wheel everywhere and giving it a jiggle. That will be the task for tomorrow.

Anyways... I never tested out the 4x4 ever since I put in the new/used transfer case which solved my sluggish resistance gas guzzling problem. So I figured to jack up the back and test it out. I did replace CV joints, axle disconnect and the actuary last year summer. I never get a service 4x4 light.

Video is uploading as we speak.

I set the switch to 4WD, put a sledge hammer on the brakes just enough for the wheels to rotate slowly and put it in D. Front wheels aren't moving. Go under, rear drive shaft rotating, front drive shaft is rotating which means transfer case is good (leaks though...). I open up the fill plug of the front diff and everything is moving inside. Never found chunks or metal shavings inside the oil. Mind you, I change that gear oil 3 times within the last 50K miles.

Either in P, D or R (forgot to do N), if I try to budge the wheels to rotate they are solid as a rock. They are locked together with no hope of turning.

So what I'm trying to find out is if the front differential POS and I would have to get a salvaged one? Even though the carrier on the inside the diff is rotating, I'm assuming a bearing on both side aren't doing it's job or something is worn out.

AND, I am assuming the wheels are suppose to rotate in the air since I've seen some off-roading videos of you guys. Just let me know what you think.

[video]http://www.flickr.com/photos/40153155@N04/9347109841/[/video]

 

[Playsinsnow]

ShawnPooh (Sorry, had to. I was misspelled earlier)


Not sure if this will help but it did for me. At the least it will give you something to read if you have not yet until Roadie and the others chime in.

Try and test it another way.
http://gmtnation.com/f79/4wd-not-working-step-inside-107/

 

[seanpooh]

Yeah, I have that picture from offroadTB downloaded and memorized. I would assume if the vehicle is started and in D and even if the axle dissconect is trashed, wouldn't the driver side wheel rotate at least?

 

[Playsinsnow]

Yeah, I have that picture from offroadTB downloaded and memorized. I would assume if the vehicle is started and in D and even if the axle dissconect is trashed, wouldn't the driver side wheel rotate at least?

Have you ran through this? If not, do so. It is what a good shop will run through...

Having 4WD(4x4) issues? Look inside! - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum

Report back. There are numerous threads about how only one wheel spins in 4wd.
Run down the checklist.

 

[The_Roadie]

I would assume if the vehicle is started and in D and even if the axle dissconect is trashed, wouldn't the driver side wheel rotate at least?

If your disconnect isn't working, the driver's wheel may stay still because it usually has higher friction, and the front diff will turn the intermediate shaft (the part that goes through a tube cast into the oil pan) twice as fast.

Quick test is to get both front wheels off the ground with the engine off, put it in 4HI mode, then turn the driver's side. If everything's working, the passenger side should rotate the opposite way.

 

[Sparky]

If your disconnect isn't working, the driver's wheel may stay still because it usually has higher friction, and the front diff will turn the intermediate shaft (the part that goes through a tube cast into the oil pan) twice as fast.

Quick test is to get both front wheels off the ground with the engine off, put it in 4HI mode, then turn the driver's side. If everything's working, the passenger side should rotate the opposite way.

This looks to me like what may be happening. In the video where he looked in the front diff as it was spinning it looked like the side gear was spinning faster than the carrier.

The disconnect acting up and the brakes lightly applied would certainly keep the front wheels from spinning at all in 4x4.

OP, is there any play at all where the CV axle on the passenger side goes into the disconnect? Any wobble?

 

[seanpooh]

So I did the test when the vehicle is off and front end is lifted. Of course my encoder motor and front actuary is working since I could hear both pitches.
I did replace both CV joints last year August along with the axle disconnect by ATP and actuary by Dorman. This year March was when I swapped out to a 60K mile transfer case and matching encoder motor.

There is no wobble in the CV joints at all.

Now when I rotate the driver side wheel, the passenger side wheel doesn't do anything. Also when I peak into the fill plug, I see a bearing/gear moving (driver side) but it's not the whole carrier like in the video.

This doesn't lead me fully to believe that the axle disconnect is at fault because when in my video I'm in Drive, both the driver and passenger sides are locked up. They cannot be rotated by hand at all. When in Park and still in 4HI, they are freed up and I then can rotate the wheels but still, driver side rotates but no action from the other.

I'm assuming that axle disconnect does have them locked together but the front diff isn't doing it's job transferring power somewhere even though the carrier is turing over.

But I do understand that the front differential is a open one and if you spin one side, then the other rotates the opposite direction.

I just thought that when I got the new transfer case in that I would finally have 4x4 back this winter. Not this winter. I guess my problem is beyond the scope of troubleshooting or I could claim a warranty issue with ATP.

I guess one last test could be for me to be certain is to remove the CV joint off the passenger side and have a friend rotate the diver side. In this scenario, if it's a fault in the front diff then I won't see the intermediate shaft rotate. If I do see rotation inside the disconnect, then it needs to be replaced.

 

[C-ya]

Looks like it may come down to removing and disassembling it. Wish I knew more about it. We're not that far apart, but this is my first 4WD vehicle and I haven't done anything like that yet.

 

[seanpooh]

Yeah, taking out the front diff wont be something I would be doing soon since I deliver pizzas for the summer most of the week.

I could swap out the front axle disconnect pretty (if it comes to that) easily since I put some anti seize the last time I changed it out. Just got to try to get it done before the Michigan winter.

The last winter that just passed I used 2wd all throughout. Its not the best driving but I still made it through the snow.

 

[seanpooh]

Guess what guys... 4X4 works!

And guess what the problem was...
...
...
...
... the actuator

I started to replace the disconnect again. I didn't put back the CV joint yet (at least half of it). I wanted to make sure the front differential was working. I told my brother to spin the driver wheel. Clearly on the inside of the disconnect I can see the shaft that runs through the oil pan rotate the opposite direction. One problem eliminated. Next was to rule out the actuator since the disconnect I put in was brand new (2nd time). Put my old actuator in, switch it to 4HI and told the bro to spin the wheel. Nothing.

We took a chips and dip break and I got to thinking.

The current actuator was brand new (doorman) from last year when I replaced the whole disconnect the 1st time. So I got my old actuator which is stock and has AAM stamped on it and bolted it in. Turned the switch to 4HI and I spun the front wheel. OMG the other side went the other direction.

Come to find out that the plunger on the Doorman model never extended all the way to lock both left and right wheels (I am assuming). It did however extend and retract as it should. Probably grease is holding it back just as Roadie suggested from a thread of his.

It has been 2 years since my 4WD worked and now it does...

Thanks guys for all your suggestions and comments. Hopefully this thread will help another guy or gal out. Just swap out the cheaper and smaller parts before moving on the the more expensive and bigger parts.

 

[The_Roadie]

Thanks for the report. Frustrating story.

The OEM actuator has a design that if the motor fails to extend the plunger, it should report that back to the TCCM which will then flash the mode light as an indicator that the actuator failed to obey its command. I never took apart a Dorman, but I have to assume they competently copied the PCB design inside the actuator.

So what's left as a possible culprit is the overtravel mechanism. The actuator's motor drives a very highly leveraged gear train to develop the force to extend the plunger. If the disconnect is broken internally, the plunger may not be able to extend fully, so there's a spring inside the plunger to absorb the force that can't be used to extend the plunger. Your disconnect could have cold grease that's increasing the actuation force, and the Dorman spring might be weaker than the OEM spring, and that might be the root cause of your problem.

The grease I mentioned in the actuator teardown thread was coating the sliding contacts on the PCB, and when the actuator got close to being extended under load, the grease prevented the maximum current from getting to the motor, so it stalled. And then the TCCM noticed it hadn't extended all the way and the TCCM light flashed. When the actuator was hanging in midair and commanded to move, it moved just fine because there was little mechanical load and the motor current stayed low and the grease had no effect. That's the precise conditions I was troubleshooting before.

 

[seanpooh]

Along with a faulty axle disconnect and the Dorman actuator, it never worked properly. I would assume that both parts together caused the wheel to "lock" and not move/rotate in my video.

Funny thing is that with those two previous parts, it never told the TCCM that a command has failed. Then again I have the original 2002 TCCM. Now that I try to remember, I never seen the Service 4WD light unless I unplugged the actuator when the vehicle is on.

But all works very well now. Time to see if I can rebuilt the old axle disconnect and maybe take a look see inside the Dorman actuator.