gmc sierra 2500hd SERVICE 4WD

[Tyler Sywyk]

So Here is Ontario we got our first snowfall this year, so I went to go move my 08 GMC Sierra 2500HD Crew Cab Long box pickup and wouldn't go as I didn't have any weight in the back... So I switched it to 4 and went to go but nothing, The 4WD switch indicator light flashed for about 30 seconds and then finally switched (Or supposably) switched to 4WD HI and the 4WD HI light was aluminated but the 4WD wasn't working so I switched from 4HI back to 2HI and it switched normally on the switch no waiting 30 seconds... and tried switching it back again and then the service 4WD message on the dash came up. i also tried putting it in Neutral and tried 4L and 4HI but nothing. Back in the summer I was in a murder situation pulling a heavy trailer uphill so I switched to 4 all good and drove out, a few mins later went to switch back flipped it and immediately on the display came up "Service 4WD System" so I just kept driving (as per I was in a time crunch) and about 5 mins later after a few jerks of emptying a dump trailer and restarting the truck it finally switched to 2HI. After that i never thought about it again until now.  I also have a loud/ quite like humming or growling noise like what winter tires would make when driving on pavement in 2HI at anything above 60 KM/h. I have bf Goodrich all terrain Tires on my truck, so I assumed it was just that. but now a little skeptical on if it is the tires or something like the transfer case. I am a good do it your self-mechanic, I don't know too much but I learn as I go, so any help is much appreciated. 

[davester]

I would suggest checking if the actuator in the front axle is functioning correctly.  It sounds like it may be stuck either in '4wd' mode or '2wd' mode.

[swathdiver]

Get a code reader and pull the codes, it will tell you what's wrong.  Can you listen for the actuators?  BFGs are fairly quiet so you may have a bad hub or something else going on, how's the front fluid?

[Tyler Sywyk]

5 hours ago, swathdiver said:

Get a code reader and pull the codes, it will tell you what's wrong.  Can you listen for the actuators?  BFGs are fairly quiet so you may have a bad hub or something else going on, how's the front fluid?

Yes, two things I forgot to mention here... I have a code reader and when I put it in to read the code it's giving me when the message comes up on the dash, there is no code. Which I found very weird. Also what I am guessing is the actuator sound I can hear it when I turn the switch to 4, it attempts just once and doesn't do it again. As for the fluid, I will check it tonight, that is the transfer case fluid you are talking about right?

[Tyler Sywyk]

6 hours ago, davester said:

I would suggest checking if the actuator in the front axle is functioning correctly.  It sounds like it may be stuck either in '4wd' mode or '2wd' mode.

So how would one go about checking this?

[sdeeter19555]

Yes, two things I forgot to mention here... I have a code reader and when I put it in to read the code it's giving me when the message comes up on the dash, there is no code. Which I found very weird. Also what I am guessing is the actuator sound I can hear it when I turn the switch to 4, it attempts just once and doesn't do it again. As for the fluid, I will check it tonight, that is the transfer case fluid you are talking about right?

Take it to Advance Auto, your code reader probably can't read those codes...

Steve
2012 2500hd 6.0l

[davester]

google "2008 sierra checking front actuator"

[swathdiver]

Do you know anyone with a Tech2?  It can see and read all codes, it's what the techs use at the dealerships to work on these trucks.  Every man should own one and they are affordable now that GM has moved on to another system for the newer autos.  Yours sounds like it wants to work but might be stuck or broke.

[davester]

Yeah, basic ODBII code readers just read basic engine codes.  Significantly more expensive ones read transmission/abs/air bag codes.

 

A knockoff techii or something like Autogenuity w GM Enhancement (Windows software + a cable to hook up to your truck) can read codes and perform diagnostics for all the computers in your truck (there are about 10-15 depending on what options your truck has).

[Tyler Sywyk]

46 minutes ago, davester said:

Yeah, basic ODBII code readers just read basic engine codes.  Significantly more expensive ones read transmission/abs/air bag codes.

 

A knockoff techii or something like Autogenuity w GM Enhancement (Windows software + a cable to hook up to your truck) can read codes and perform diagnostics for all the computers in your truck (there are about 10-15 depending on what options your truck has).

The code reader I own is an Autel MaxiDiag MD801 PRO

[Tyler Sywyk]

2 hours ago, swathdiver said:

Do you know anyone with a Tech2?  It can see and read all codes, it's what the techs use at the dealerships to work on these trucks.  Every man should own one and they are affordable now that GM has moved on to another system for the newer autos.  Yours sounds like it wants to work but might be stuck or broke.

I made some time to make a video narrowing down what is wrong with it tonight, but i dont know how i would post it as the video size is 80MB. 

[swathdiver]

Host it on youtube.

[Tyler Sywyk]

55 minutes ago, swathdiver said:

Host it on youtube.

Youtube link is:

 

[davester]

When you switch it to 4wd, and try rotating the shaft, it feels like the transfer case is stopping it from rotating?

 

And with the light flashing in the interior, and with it not engaging 4wd, it most likely is the actuator in the front axle (with a smaller possibility of it being the wiring).

 

Unscrew it from the front axle (there may be some oil that comes out, you might want to lift up the passenger side a bit more than the drivers side), and then watch it while shifting between 2 and 4wd.  It should extend when going into 4wd, and you shouldn't be able to stop it from extending, and then retract when going to 2wd.

[Tyler Sywyk]

17 minutes ago, davester said:

When you switch it to 4wd, and try rotating the shaft, it feels like the transfer case is stopping it from rotating?

 

And with the light flashing in the interior, and with it not engaging 4wd, it most likely is the actuator in the front axle (with a smaller possibility of it being the wiring).

 

Unscrew it from the front axle (there may be some oil that comes out, you might want to lift up the passenger side a bit more than the drivers side), and then watch it while shifting between 2 and 4wd.  It should extend when going into 4wd, and you shouldn't be able to stop it from extending, and then retract when going to 2wd.

So what am I unscrewing?