2008 3500 with dead 4wd

microsuck · 11-02-2009, 06:15 AM

So this truck only has 12k miles on it. Yesterday I ended up in a soggy field and only the rears were turning. I put it in 4Hi, and the light changed over like it should, but the front wheels wouldent turn. I reversed and forwared transmission a few times, spinning the rears each time. Fronts would never turn though. Same when I tried 4Lo. Is there something I should check? I want to avoid warranty work if possible. I am going to put it on the jack stands tonight and see of the transfer case is spinning the front drive shaft.

**ob_1jr** · 11-02-2009, 06:20 AM

sounds like the encoder motor not enguaging. (although i think you would have some code or light if this did happen, but stranger things have happened) I dont know why you would want to avoid warranty work as it should be under warranty and fixed for free. I pay that much for a truck and something doesnt work...the dealer is getting it back until it does work....Each to his own.

**Six-Gun-Todd** · 11-02-2009, 06:29 AM

First check to see if the front half shaft is spinning the front differential yoke. If it is you can narrow your search down to something in the front end.....more than likely the actuator that engages the passenger side axle shaft to the differential.

microsuck · 11-02-2009, 06:44 AM

Is there a good write up on how the GM 4wd system works? I have been checking all morning. I havent had a GM truck before, only Dodges with the manual 4wd system.

I am going to put it on jack stands and inspect it, but not touch anything. Any idea what to look for? Or feel? I would expect something would click somewhere when 4hi is engaged.

**Six-Gun-Todd** · 11-02-2009, 06:48 AM

Quote:

Originally Posted by microsuck

Is there a good write up on how the GM 4wd system works? I have been checking all morning. I havent had a GM truck before, only Dodges with the manual 4wd system.

I am going to put it on jack stands and inspect it, but not touch anything. Any idea what to look for? Or feel? I would expect something would click somewhere when 4hi is engaged.

With the truck in the on position (not running) switch the 4x4 gauge into 4hi and check the front half shaft. It should be static with the truck in park......now move to the front tires and see if they spin.....if they don't spin in opposite directions it's more than likely the actuator. It's a white plastic plug in the passenger side axle housing......very easy to replace.

microsuck · 11-02-2009, 07:03 AM

Awesome, I am going to try that when I get home. So my understanding is this, tell me if I am right so far.

There are two selonids/motors for 4wd operation. The Encoder Motor on the transfer case that sends power to the front shaft. And the Actuator Motor, which joins the two front axle halves together. Either one could have failed, but the way to check is to see of the front differential input shaft turns on 4wd, and then also test if the front axle halves are locking together.

jaydawg · 11-02-2009, 07:08 AM

Take to dealer!!! Can be an issue with BCM not seeing signal....you might do more damage than troubleshooting. Use your warranty....us techs are starving for any work....

microsuck · 11-02-2009, 04:24 PM

Very interesting. I put it up on jack stands and it works now. Wonder why it didnt work in the mud this weekend? The only thing I did in between then is pull fuse #13 TRANS IGN 1 and then put it back in. Just to see if it was blown, it wasnt. Not sure what its for, but it was the only thing that seemed like it was for the transmission.

**Six-Gun-Todd** · 11-05-2009, 06:34 AM

Quote:

Originally Posted by jaydawg

Take to dealer!!! Can be an issue with BCM not seeing signal....you might do more damage than troubleshooting. Use your warranty....us techs are starving for any work....

HAHAHA.....wish I could when something hits the fan but that's what happens when you want to go fast.....you take responsibility for your actions. (Or at least I do

)

ChaseN · 11-05-2009, 07:44 PM

take it to the dealer man!