Buick AWD stuck in 4WD

[ruggles]

I have a 2006 Buick V8 AWD, so no switches. If I turn into a parking space or other slow tight turning, it hops around on the front wheels, and mileage is bad.

I have had the front wheels off the ground and the front drive shaft is locked to the transfer case but front diff is quiet and smooth (no spline disconnect)

Also lifted just the rear wheels and idled the rear wheels so that they were both spinning and while it wanted to creep forward, it did not activate the 4WD lights on dash. The rear wheels may not have been spinning fast enough. While driving, I have broken one wheel free and the traction control light came on while driving but no snow here, so difficult to break both rear wheels free.

No lights on dash are activated and dealer says no codes. They wanted to change the Transfer case fluid which is now the second time in 78000 miles.

Should the dealer be able to tell if the TCCM is sick ?

Should the Dealer be able to tell if the actuator is lazy or stuck?

Trying to determine if I should go elsewhere or if it's just hard to diagnose.

I suspect the clutches are partially engaged and this will lead to a failure soon.

Any comments appreciated, but this is and AWD, not and Envoy or TB.

 

[RayVoy]

Your clutches are always partially engaged, about 5%.

You have somewhat proven your suspicions and also the dealer's suggested fix.
When you raised the rear and found the front shaft felt connected to the t-case, that is normal; when the truck tried to pull forward, that is normal; the binding (as you know) is not normal. The good news, is that fresh fluid should fix the problem.

 

[ruggles]

So I did what any self respecting DIYer would do: crawled under it and took it apart.

With it out you can twist the spline that activates things and with one front wheel off the ground some time it would turn and sometimes it would not, so it's seems clear to me the transfer case is not a problem.

You don't even have to remove it, just slip it back and twist it. It seemed spring loaded

So now either the actuator is bad, the sensor inside it is bad or the TCCM is not sending good info to the actuator.

Any good way to test the activator motor off the car?

 

[RayVoy]

OK, so you removed the encoder motor, this relieves the pressure on the clutch packs.

I don't think (as I said before) that you have anything in the transfer case that needs to be fixed, but you might require a fluid change.

The front diff is designed so that it will allow the front wheels to turn, in different turning radiuses (radii), one of the front axles is connected (through the diff gears) to the front driveshaft. The front turning circles are always different from the rear; therefore, the front driveshaft rpm will be different than the rear driveshaft rpm.

The job of the transfer case is to connect the two driveshafts (if front power is required), or to let the two driveshafts turn without binding (when front power is not required).

Your not the first, on this forum, to have this problem, the fixes have usually been a fluid change, an encoder motor change, a new t-case controller and a t-case rebuild. The last 3 usually set a t-case code that the dealer can read.

 

[ruggles]

Well since my favorite stealer wants over $400 for the encoder motor, I'm not going for that without some indicator, and no codes when he looked yesterday.

 

[The_Roadie]

When the dealer hooked up his Tech II tool to look for codes, he could have also commanded the encoder motor to run through its entire range of motion and confirm the unit was bad. If they did that, then you can trust the diagnosis. If they failed to do that, then they had no justification to quote you for the encoder motor replacement.

They can be had for $100-175 on Ebay and parts stores. Find an independent mechanic to change it if you don't feel like doing it.

 

[Jkust]

, it did not activate the 4WD lights on dash.

Hold on a sec...there is no specific 4wd light on the Rainier or any of the A4WD equipped 360's???

 

[ruggles]

Just returned from drive around with service manager and Tech2. He pulled all codes from all modules. There were several lost communication and the steering wheel position codes. We decided to clear them then we pushed it around on gravel to see if they would recur. It did not feel like it was engaging front wheels (completely) as it fishtailed. He agreed there should have been more stuff thrown up in front, but no codes.

Turned the steering wheel lock to lock to see if it would trip the steering wheel position sensor code, and floored it while wheel straight and/or partially turned. I asked if he did all the checks of the ATC which he said he did. He said the sensors were reporting on the front and rear shafts (these are not the ABS wheel sensors), and all else looked good. I was driving so did not see all of this. Still no codes.

As far as "commanded the encoder motor to run through its entire range of motion and confirm " he did this while in parking lot. He saw nothing amiss and I heard nothing while standing outside vehicle. I asked if it were appropriate to do that check with actuator removed from Transfer Case. He was concerned about actuator moving outside the range of it's motion.

re: lights. This has Traction control, Stabilitrak, and AWD. There is a thumb button on the shifter that if held for a second turns off Traction Control, and if held for 5 secs turns off Stabilitrak. This seems to function as far as turning off and back on and no warning lights stay on after starting car. THe ABS has worked recently.

There is also the service AWD light (Wrench next to 4 tires with 2 front tires turned). I also have the DIC which does not indicate any errors. It has said SERVICE STABILITRAK several times in the past 3.5 years but does not stay on when I turn off and on the car (which the book says to do) and I attribute this to confusion during startup of the car (turning the wheel or touching the button on the shifter, etc) We also have a CTS and this has some quirks also when doing too much just after starting the car.

The traction control does activate (light comes on and then turns off) in the gravel. I don't think there is even a light or DIC message for the AWD, it is completely automatic with no switch.

I removed the actuator and drove with it, which was more pleasant with no hopping on turns. This made the service AWD light stay on.

I will order the actuator from RockAuto for $150 delivered. It seems to be holding the clutch partially engaged but never releasing totally or it is stuck partially on.

Does anyone know if the servo motor (actuator) supposed to be variable? like tighter on the clutch at higher speeds or with the wheel straight??

 

[Jkust]

re: lights. This has Traction control, Stabilitrak, and AWD. There is a thumb button on the shifter that if held for a second turns off Traction Control, and if held for 5 secs turns off Stabilitrak.

It has said SERVICE STABILITRAK several times in the past 3.5 years but does not stay on when I turn off and on the car (which the book says to do) and I attribute this to confusion during startup of the car (turning the wheel or touching the button on the shifter, etc)

The traction control does activate (light comes on and then turns off) in the gravel. I don't think there is even a light or DIC message for the AWD, it is completely automatic with no switch.

QUOTE]

Right so then the stabilitrac has it's own light, the traction control has a different light but the AWD activating has no dedicated light. When they both (stabilitrac & tcc) activate the DIC reads 'stabilitrac active' plus the dash light lights up but again nothing specific for the AWD (since no indicator was included).

As for the service stabilitrac message, that is generally caused by the steeringwheel position sensor which then needs replacing. I've had two Rainiers and the current one gives that same message every now and again. We all generally know about the ability to shut both systems off with the shifter button since its the only was you can have any fun. I'm curious as to this issue as well since I'd swear there are times my 9-7x AWD is sticking on as well but have never proven it. Only on wet days taking one particular hairpin turn in my parking ramp where the cement is wet but not slippery it hops. It has no business locking up at 1mph on wet but grippy cement.

 

[ruggles]

jkust, if you're bored and wanted to go to the vehicle, and jack driver side front wheel off the ground, would it turn easy, turn hard or just appear locked to the other wheels?

The service manager said it should not turn, because the clutch supposedly has it partially engaged. Mine turns easy with the actuator off the Tcase.

 

[RayVoy]

No lights on dash are activated and dealer says no codes. They wanted to change the Transfer case fluid which is now the second time in 78000 miles.
.

^^^^ Your first post.


You seem to be going to a lot of trouble to avoid trying the dealer's original suggestion. What did the "drive around" with the service manager cost?

 

[ruggles]

Not at all. I changed the fluid when I bought it at 58k, and they did it on Wednesday. Otherwise no suggestion from dealer.

 

[RayVoy]

and they did it on Wednesday. .

Sorry, your first post suggested they wanted to change the fluid and you did not think it was a great idea.

If you updated us later, I missed it.