4WD not working? Step inside.

[TJBaker57]

I am not familiar with the newest 4wd systems but, should the front drive shaft spin freely while locked into 4wd on my 05 Chevy Trailblazer? The vehicle is on the ground and in Park while testing. In older vehicles the front drive shaft doesn't spin but, I am very unfamiliar with these newer setups. The front actuator and encoder motor on the transfer case are making the noises that they should but, still have no 4wd. The lights for the 4wd switch are working and it is lighting up in each selection.(2WD, A4WD, 4HI, 4LO)

Most of what you need to diagnose your issue is already in this thread.

Short answer: no. Your front driveshaft should not be free to turn in 4WD. My best guess is your front axle disconnect is nit working. There are ways it can fail that won't affect the indicator lights at the mode switch.

 

[Wooluf1952]

Welcome

In case you haven't heard:
https://gmtnation.com/forums/threads/welcome-to-gmtnation-com-heres-the-story.218/

The truck will not go into 4LO while in Park. Also there are times that the truck has to move (only a few feet) to engage 4HI.

 

[jbeitz107]

I appreciate the feedback. Let me try to be clear about the responses. I remember in the old days(YES I am old) that the transfer case would lock in and the front drive shaft would not spin even if the front end isn't locking in. Yes, I am referring to an older 4wd setup. But, is this also true with the 05 Trailblazer transfer case? I have a friend with a dealership that has a transfer case out of the vehicle and it is currently locked in 4wd but, the front output shaft spins at the same rate as the rear shaft hence will not spin if the rear is not spinning as if in Park. I have run the vehicle for more than a few feet but, only the rear wheels will spin. I have read many forums and there is something about the A4WD taking out the front end of the transfer case. I am unclear of what happens in this case. Can someone clarify if the front drive shaft would spin even with the transfer case locked in 4WD(after moving over 10 ft.) and what would the next steps be in diagnosing this issue. I am in no way a mechanic and have limited funds to resolve this issue but, I need to be able to get back and forth to my doctor appointments during the winter.(Have had to cancel many of them due to this issue and snow fall. Not looking for pity but, would appreciate a helping hand.)

 

[jbeitz107]

I figured it out. The transfer case is alright. It is the front end. Thanks guys.

 

[jbeitz107]

Ok found out the transfer case is fine. How do I know what the problem with the front end is? Is it the actuator housing or the entire diff? Any clues on this? Thanks guys.

 

[TollKeeper]

Found this on youtube today. the mechanic is so wrong on this.

 

[jbeitz107]

@TollKeeper - Thanks but, in my case there is no noises coming from the front end other than the actuator engaging. I believe that the actuator housing is the issue in my case but, could be wrong. Thoughts on this situation are welcomed.

 

[TollKeeper]

@jbeitz107 - Im sorry man didn't realize there was am active problem going on, was replying to the thread and not you directly. Let me get home to my computer and i will look over your problem and see if i can help.

 

[jbeitz107]

Thank you. That is the bad thing about buying a used vehicle. 171k when bought so I know that I am buying a headache. At least once the 4wd issue is fixed it will be great. It is the only problem that I am having after replacing the transmission. LOL

 

[TollKeeper]

So the simple answer is NO, you should not be able to spin either front wheel, while the other is on the ground, with the truck in 4wd (not A4wd).

Now the question is, whats not engaging....

With all 4 wheels in the air, engine running, the truck in 4wd (not A4wd), does the front and rear drive shaft spin when put in gear?

Truck off, transmission in neutral (still in 4wd), if you spin the front drive shaft by hand, does the rear drive shaft spin?

If you put it in A4wd (not 4wd), raise one front wheel in the air, spinning the front drive shaft by hand, does the front wheel in the air spin?

With the truck in 4wd (not A4wd), if you raise the front of the vehicle, and spin either wheel, does the opposing wheel spin in the opposite direction?

Report back on your findings from these tests, and I believe we can give you a very positive answer.

 

[jbeitz107]

The transfer case is working correctly. Seems to be an issue with the front end locking in. But, there is no clunking noises or grinding noises from the front end. The issue is that I got this vehicle used so I didn't know what happened that led up to this. I will have to check the vehicle with the front end in the air next to test the 4wd. Thanks for the thought. Do you think that the actuator housing could be bad and not engaging? That is my next step in my opinion but, could be wrong. Again thank you TollKeeper for all the help thus far.

 

[TollKeeper]

It could be just the encoder motor, or the internals on that unit could be bad. Quite a few members have had to replace the entire unit (myself included). Another thing to check, jack up the passenger side of the truck, pull the tire off, and grab the inside cv joint. Can you move it up and down or side to side? If you can, the alignment could be off enough that it cant engage. Which would mean a replacement of the cv axle engager thing (cant remember what its called at the moment).

 

[jbeitz107]

The actuator housing I believe it is called.

 

[m.mcmillen]

The intermediate shaft that goes through the oil pan has been known to strip out on the end where it connects to the axle disconnect (The part bolted to the passenger side of the oil pan.

 

[TollKeeper]

Although thats true @m.mcmillen , he did say he wasnt hearing any noises, but I dont remember if he said that was while driving, would have to wait for him to report back on that on.

@jbeitz107 , if you put it in 4wd, with all wheels on the ground, and turn the wheel hard over, do you get any crow hopping, or snapping noises?

 

[m.mcmillen]

I replaced a shaft and disconnect in one that my father in law bought used. With all four wheels off the ground and in gear the front drive shaft was turning but no noise was up front. The end of the intermediate shaft was worn smooth.

 

[jbeitz107]

@TollKeeper - No there are no noises coming from the front end or popping at all. It acts as though it isn't even trying to engage at all. @m.mcmillen how likely is this to happen. And what cost am I looking at for the parts to fix this. Can you give me an idea of the parts required?

 

[TollKeeper]

Get those other tests performed, and we can give a better answer

 

[Matt]

Is the Service 4WD light on?


Yes: Go to Section 1.


No: Go to Section 2.






Section 1: My Service 4WD light is on.


Are there any lights lit on the 4x4 selector switch?


Yes: Go to Section 2.


No: Try these steps.
With the ignition off, rotate the 4x4 selector switch from left (2HI) to right (4LO) and back again about 20-30 times. With lack of use, the contacts inside the 4x4 selector switch can get a light amount of oxidation on them. Repeatedly rotating the switch can sometimes clear this problem up. If this doesn't help, read step 2. If step 2 doesn't work for you, replace your 4x4 selector switch. If replacing the 4x4 selector switch doesn't work for you, try to find a local member with a verified working TCCM to swap in. If the problem goes away, return your friend's TCCM and buy a replacement for yourself. Search these forums for replacement instructions.


On some 2002 model year trucks, the Transfer Case Control Module (TCCM) can have trouble waking up when the engine computer tries to talk to it. Fuse #8 in the engine bay fuse block provides power to the TCCM. Pulling this fuse and replacing it will usually wake the TCCM up and allow the use of 4WD for a time. Fixing this requires either a dealer software update (can be spendy, doesn't always work) or replacing the TCCM with a unit from a 2003 or newer model with selectable 4WD.




Section 2: Checking the motors.


With the ignition on, switch the 4x4 selector switch from 2HI to 4HI. You should hear two distinct mechanical whirring sounds. One from the middle of the truck (under you) and one from the front of the truck.


I hear both whirring sounds: Go to Section 3.


I don't hear the sound from under me: There is an issue with the Transfer Case Encoder Motor. Check the connector going to the motor(cylinder looking thing) on the transfer case for damage/corrosion. The motor may require replacement.

I've highlighted my issue in red. Short story: Service 4WD light on, no lights on switch. Switch was replaced last year with one Grimor gave me. I went to O'Reilly's and got a new switch, still no lights. Replaced the TCCM from an 03 that I had in it with one from an 06 that I got a couple of weeks ago. Still nothing. Took out fuse #8 and replaced, still nothing.

I'm guessing the encoder motor has had the dick? Which would suck because I replaced the actuator/encoder assembly as a whole with a new US Powertrain one about 3 years ago.

 

[budwich]

you might be wise to get someone with a reader that is capable of reading ALL codes to find out what the service 4wd reason is. Replacing parts blindly might be an answer ONLY IF the problem is NOT wiring related. Perhaps even doing some bench checks on the encoder motor might help narrow the problem down.

 

[Mooseman]

Agreed. You need to get the codes. It's unusual for the lights to go off right off the bat without doing anything. Only time I ever saw that was when the '02 TCCM was bad. Sounds like a power or wiring issue or possibly the encoder or disco actuator is shorted out.

 

[Matt]

Got the code: C0327. So it seems it's an electrical issue with the encoder motor from what I can gather in my research. I'm not good with electrical stuff at all. I have a meter and can do basic check voltage stuff with the battery, but this has me scratching my head on where to start.

 

[TJBaker57]

@Matt what year is your Trailblazer? If an early model and you have a elm327 clone or similar then CarGauge Pro will get you those codes

 

[TJBaker57]

@Matt here is a pretty good writeup on the c0327... Not specifically for our platform but the concepts are the same. Wiring colors may be different though, not sure on that.

What does a C0327 code mean on a GM vehicle

A C0327 code on a GM relates to a problem with the transfer case motor or wiring. Here's how to diagnose the problem

ricksfreeautorepairadvice.com

 

[TJBaker57]

@Matt also be aware that if it turns out the encoder/motor assembly is at fault and you're willing to do a little more work, the sensor inside the assembly is replaceable for a lot less money. But you must be certain that the rest of the assembly is OK first.

DTC C0327 Resolved

So after many years of occasional issues with the transfer case shift motor encoder I decide to fix the damn thing. Hooked up the Tech 2 to display the encoder return voltage and take it under the truck with me. Wiggle this, push pull that, tap here and there all the while watching that return...

gmtnation.com

 

[Matt]

@Matt what year is your Trailblazer? If an early model and you have a elm327 clone or similar then CarGauge Pro will get you those codes

Mine's an 02 and that's what I used to get the code.

 

[Matt]

Update: seems the cold was an issue as it's corrected itself for the time being. I'm going away on Sunday so I'll leave it go until the spring when I can dig round the wires and see if I can tell what's really going on.