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4WD Issue

DW2018

By DW2018
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DW2018 New Member

DW2018

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Posted

When I turn the knob to engage the 4WD the indicator light indicates it goes into 4WD. However, the front wheels do not actually turn. Once the truck flashed a service 4 wheel drive message- but that was once it was not working for months with no message and message is now gone again.

 

Took it to the mechanic they said- they went through everything and its in the front axle they would have to drop the axle and take it apart to figure out the specific part.... I am a bit confused what that means now that I think about it- it is a 2011 GMC Sierra 2500- it has IFS not a straight axle?

davester Senior Enthusiast

davester

Posted
Posted

Yes, you need a mechanic that can actually diagnose what's going wrong, as your mechanics idea of ripping apart the front diff to look for a problem is more of a "how much money can we get from this guy" kind of thing.

 

It's far more likely to be a simple actuator, sensor or wiring problem than it is to be internal bits of the transfer case or front diff, and it's pretty straightforward to determine where the problem is (encoder on the transfer case, sensor on the transfer case, actuator on the front diff, or internal bits in the transfer case or internal bits of the front diff).

 

Drive away from that mechanic, put a note in the contact page on your phone for that mechanic to never go there again, and find another one.

tlaw91 Enthusiast

tlaw91

Posted
Posted
Yes, you need a mechanic that can actually diagnose what's going wrong, as your mechanics idea of ripping apart the front diff to look for a problem is more of a "how much money can we get from this guy" kind of thing.
 
It's far more likely to be a simple actuator, sensor or wiring problem than it is to be internal bits of the transfer case or front diff, and it's pretty straightforward to determine where the problem is (encoder on the transfer case, sensor on the transfer case, actuator on the front diff, or internal bits in the transfer case or internal bits of the front diff).
 
Drive away from that mechanic, put a note in the contact page on your phone for that mechanic to never go there again, and find another one.

That’s so much better then the short answer I put [emoji23]
Thanks davester!
DW2018 New Member

DW2018

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18 hours ago, davester said:

Yes, you need a mechanic that can actually diagnose what's going wrong, as your mechanics idea of ripping apart the front diff to look for a problem is more of a "how much money can we get from this guy" kind of thing.

 

It's far more likely to be a simple actuator, sensor or wiring problem than it is to be internal bits of the transfer case or front diff, and it's pretty straightforward to determine where the problem is (encoder on the transfer case, sensor on the transfer case, actuator on the front diff, or internal bits in the transfer case or internal bits of the front diff).

 

Drive away from that mechanic, put a note in the contact page on your phone for that mechanic to never go there again, and find another one.

Mechanic did diagnosis...they said they went though everything "easy" and determined there were no problems there-it was in the front end that it would be a lot of time in labor just to take it apart and get it back together and asked if I wanted to bother, this was last year and I said no so not something they were getting money from- and they are always booked so dont think its a money thing at all....also it was a one owner vehicle before me I bought it from a dealer with a 30 day warranty/over 100k miles and didnt find out the 4 wheel drive didnt work until a month later when i got my horse trailer stuck at a horse show... so dealer wouldn't do anything about it and I suspect original owner got rid of it because they busted the 4WD and knew it and know Im suspecting they knew it was going to be a pricey fix... just trying to figure out if its anything we can tackle on our own

 

davester Senior Enthusiast

davester

Posted
Posted

Start with something simple.  Put it in 4wd, drive a couple of feet, and lift one of the front wheels off the ground.

 

If you can't spin the lifted wheel: success, it's in 4wd

 

If you can spin the front wheel, then reach under the truck on the driver's side, and try spinning the driveshaft going from the transfer case to the front diff by hand.

 

If you can spin it, then the transfer case didn't get into 4wd.

If you can't spin it, then the front diff didn't lock.

 

davester Senior Enthusiast

davester

Posted
Posted

...and if the mechanic actually did diagnose that there is a problem inside the front diff (ie, that the transfer case is shifting into 4wd, and the actuator in the front axle is working, and using a short rod with the actuator out doesn't lock the front diff, the common parts to break are

-the sliding locking gear

-the passenger side stub axle

 

Both are straightforward to fix, and the only special tool you need are snap ring pliers (besides wrenches), and you can do it by splitting the diff in the  truck (so you don't drop the whole diff, just unbolt the passenger side of it.

 

Alternately, just hit a junkyard, find another truck with the same diff (so gmt900 truck, that's a 2500/3500, and has the same gear ratio that your truck has) and bolt it in

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DW2018 New Member

DW2018

Posted
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Posted
17 hours ago, davester said:

...and if the mechanic actually did diagnose that there is a problem inside the front diff (ie, that the transfer case is shifting into 4wd, and the actuator in the front axle is working, and using a short rod with the actuator out doesn't lock the front diff, the common parts to break are

-the sliding locking gear

-the passenger side stub axle

 

Both are straightforward to fix, and the only special tool you need are snap ring pliers (besides wrenches), and you can do it by splitting the diff in the  truck (so you don't drop the whole diff, just unbolt the passenger side of it.

 

Alternately, just hit a junkyard, find another truck with the same diff (so gmt900 truck, that's a 2500/3500, and has the same gear ratio that your truck has) and bolt it in

thank you

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