Front differential acuator?

[TilliamWe]

A co-worker has a 2001 (I think) GMC Sierra 1500HD 4wd. Push button 4wd, of course. Here is what he describes:

"The service 4 wheel drive light came on and the indicator light on the switches went off...so I changed the switch and still no fix and then it was engaging into 4wheel without knowing but could tell by gas miles.. Then the next time you started it it may be back in 2wheel its like the lotto you just never know...as far as getting worse no stayed the same "

That sounds like the front diffential acuator to me. Is that what it sounds like to all of you? I unplugged it Friday morning for him and he says it hasn't tried to engage into 4wd since. But I don't know how much he has driven the truck either.
I know there is an acuator on the transfer case as well, but it's a lot more expensive. And I know from others' past experiences that the front acuator goes bad, a lot. I don't have experience with this push button system, though. I just don't want him to keep buying parts, I'd like to fix it the first time out.
So what say you all? Are this the classic symptoms of the front differential acuator's failure?

 

[CVX20SPRINT]

Re: Front differential acuator?

It usually is the electrical connections gone bad in the actuator motor on the side of the transfer case.Switches on the side of the motor send a signal to the module to tell it what position it is in(2wd,4wd etc...).Water intrusion and corrosion screw up the signal.I have seen some of the older ones taken apart and cleaned up with some success,but you will probably end up replacing the motor.I haven't worked at the dealer since 2000,but that was the most common failure then.If the frt axle actuator fails the frt axle won't lock up(a failure by it won't keep the axle locked in).The transfer case could be in 4wd,but it won't give you 4wd until the frt axle locks in.

 

[Bifflefan]

Re: Front differential acuator?

If there is a service light on, then there is a code in the ECM that should tell you the problem. You can go to AutoZone and they can read the codes for free. Then once you get it fixed, they can hook back up to it and you can clear the codes. Around here they wont clear them for you.

 

[scca vette]

Re: Front differential acuator?

http://findarticles.com/p/articles/mi_qa3828/is_200406/ai_n9424000/

This might help you! I agree it is probably the accuator being as they are a known problem with these trucks, I have replaced a few myself.

Good Luck

 

[Mntom]

Re: Front differential acuator?

EDIT

You know, it is posts like this that turn people off to these forums.

 

[tx1961whaler]

Re: Front differential acuator?

EDIT

Please read and respect the Forum rules.

 

[TilliamWe]

Re: Front differential acuator?

Excellent info guys, thanks a ton. I was worried that you would tell me it's more likely the transfer case one. It's over $270, when the front actuator is less than $100. I'll have my co-worker get the codes read and see if it says anything of any use.

BTW, what in the world happened that got deleted on this post? I mean seriously, it's just a "simple" mechanical question, nothing controversial here. I thought?!

 

[tx1961whaler]

Re: Front differential acuator?

Had nothing at all to do with differentials at all.....

 

[Mntom]

Re: Front differential acuator?

BTW, what in the world happened that got deleted on this post? I mean seriously, it's just a "simple" mechanical question, nothing controversial here. I thought?!

It was a post that was very political in nature that would have the ability to cause lots of tempers to flare. Thanks jb for the moderating.

 

[CVX20SPRINT]

Re: Front differential acuator?

The front axle actuators were a problem,but it is definitely not your problem.I agree about getting the codes from it.My money is still on the motor on the transfer case being the most likely cause.
The signal for the front axle actuator comes from a switch on the transfer case,so unplugging it is not really proving anything.If the front is locking in 2wd it is getting a false signal from the transfer case to engage.

 

[TilliamWe]

Re: Front differential acuator?

If the front is locking in 2wd it is getting a false signal from the transfer case to engage.

You are the second guy to state that more or less, and it makes "perfect" sense to me. I think my co-worker isn't able to tell the difference between the the front axle being engaged or not engaged. I have/will forward all this info to him, so he can see about reading the codes. If the code pinpoints the transfer case actuator, I'll replace it for him. Thanks!
The two reasons I unplugged the front diff actuator is because my experience has been with 4wd systems that have the floor mounted lever (so that transfer case actuator didn't exist or at least not in this current form), and I was easily able to reach the front diff actuator, as I lay on the ground in the county jail's parking lot, with a gun belt, 2 extra clips of ammo, and a loaded 40 caliber handgun stick out of my holster!

 

[CVX20SPRINT]

Re: Front differential acuator?

Just trying to help.Keep us posted.I personally thought the old system was way better,but people complained that the lever was too hard to move so they move it for you.When I left the dealer the Encoder motor was $600 and the Module was $400.Not sure about the switch.That was 10 years ago.The only thing that failed on the old system was the frt axle actuator.

 

[TilliamWe]

Re: Front differential acuator?

Just trying to help. I personally thought the old system was way better,but people complained that the lever was too hard to move so they move it for you.The only thing that failed on the old system was the frt axle actuator.

You did, and I was meaning that since you seconded the first guy I was convinced.
I personally LOVE having a big ol' lever on the floor to pull on. (The S-10's lever was easier to pull, though) No doubt whether you've got it where you want it!
That's the era I was coming from, that front acuator was the only thing to go bad, that's why I didn't realize the possibility of the transfer case one.

My co-worker thinks we're gonna have to drop the drive shaft and the transfer case to change it. (I haven't seen it yet) Has that been you guys' experiences?

 

[rbh]

Re: Front differential acuator?

"For what it is worth as a side note"
The wife has a 91 ranger with the electrical transfer case set up.
If she does not engage and disengage it a couple of times in the summer, it is a bear to engage in the winter when she needs it.
And yes I like manual everything.

 

[CVX20SPRINT]

Re: Front differential acuator?

Pretty sure it will come out without taking anything else off.If anything you might have to undo the frt driveshaft at the transfer case end and just let it hang down.Undo the 3(I think)attaching bolts,undo the electrical connector and slide it strait out off of the shiftshaft.

 

[TilliamWe]

Re: Front differential acuator?

Sweet!