Z71-No 4wd

ltljon · 09-12-2007, 06:57 PM

Mine is a 99, push button. All buttons light up correctly when trying to engage 4wd, no warning or flashing lights on the dash go off. You can hear an electric motor engage on either the transfer case or front differential. When driving it engaged you can feel the front end "fighting" just like any 4wd does when working right. It does not pull, make any clanking or bad noises though. I even jacked the front end off ground & no movement.
Anyone ever dealt with this before?

777stickman · 09-12-2007, 07:24 PM

Quote:

Originally Posted by ltljon

Mine is a 99, push button. All buttons light up correctly when trying to engage 4wd, no warning or flashing lights on the dash go off. You can hear an electric motor engage on either the transfer case or front differential. When driving it engaged you can feel the front end "fighting" just like any 4wd does when working right. It does not pull, make any clanking or bad noises though. I even jacked the front end off ground & no movement.
Anyone ever dealt with this before?

OK: I read your post about 10 times. Went and got a 2nd beer and read it 10 more times. And I'm still confused!!!!!

If you jack the front end up and it's in 4wd and you put it in gear and expect the front wheels to turn it ain't gonna happen if the back wheels are still on the ground.

So, what exactly is your issue, as from reading your post it sounds to me that all is good.

ltljon · 09-12-2007, 10:16 PM

Quote:

Originally Posted by 777stickman

OK: I read your post about 10 times. Went and got a 2nd beer and read it 10 more times. And I'm still confused!!!!!

If you jack the front end up and it's in 4wd and you put it in gear and expect the front wheels to turn it ain't gonna happen if the back wheels are still on the ground.

So, what exactly is your issue, as from reading your post it sounds to me that all is good.

Sorry, I said that backwards! I jacked up the rear to see if the front would pull while on the ground (in 4wd) & it wouldn't. I've also gotten it in loose pea gravel on a hill & it will just spin the rear.
Maybe I shouldn't have had my second beer before posting!

saskgmtech · 09-12-2007, 10:45 PM

there is an actuator on the front diff, passenger side to engage the front axle.....sounds like your encoder motor is engaging the transfer case, jack all four wheels off the ground and check to see if your front drive axle is turning the front drive pinion......sounds like it's either the actuator or the diff itself

777stickman · 09-13-2007, 10:57 AM

4 button (auto) or 3 button system? One more ? Even though the front is not pulling in 4wd, on dry pavement in slow turns, it feels like it's in 4wd? And does it feel the same in 2wd?

ltljon · 09-13-2007, 12:06 PM

Quote:

Originally Posted by 777stickman

4 button (auto) or 3 button system? One more ? Even though the front is not pulling in 4wd, on dry pavement in slow turns, it feels like it's in 4wd? And does it feel the same in 2wd?

4 button Automatic
Feels like both front wheels are locked together as it would if 4wd was working.
Does not feel this way in 2wd

weo38 · 09-13-2007, 12:24 PM

So if I read this right you push the auto button for the 4wd and you can hear the diff engage? Then if you jack the back up it will not pull the truck? I think the auto 4wd only engages the front wheels when a loss of grip or traction is felt. So in normal driving conditions it drives like a 2 wheel drive truck until the loss of traction is sensed. I think that's what you are asking(?). Hopefully someone will clarify the auto button to be sure.

ltljon · 09-13-2007, 12:58 PM

Quote:

Originally Posted by weo38

So if I read this right you push the auto button for the 4wd and you can hear the diff engage? Then if you jack the back up it will not pull the truck? I think the auto 4wd only engages the front wheels when a loss of grip or traction is felt. So in normal driving conditions it drives like a 2 wheel drive truck until the loss of traction is sensed. I think that's what you are asking(?). Hopefully someone will clarify the auto button to be sure.

I said Auto meaning Automatic Transmission. Sorry for confusion there.

4 buttons: Auto 4wd, 2 hi, 4hi, & 4 lo.

With rear of truck jacked up & rear wheels spinning (in any position of 4wd), this would be considered a loss of traction & the front should be trying to pull if any of the 4wd buttons are engaged, correct? This is what I would think anyway but I'm no expert.
Like I'd said earlier it wouldn't pull while I was on the loose gravel on an incline. Just the rear wheels dug in but no noise from the front.
I'll check out the sensor mentioned earlier but any & all suggestions appreciated.
Like most folks, I'm hoping for a cheap & quick fix but it rarely is!
Thanks for all the help so far.

777stickman · 09-13-2007, 08:53 PM

Quote:

Originally Posted by ltljon

4 button Automatic
Feels like both front wheels are locked together as it would if 4wd was working.
Does not feel this way in 2wd

That is really wierd because it sound as though the 4wd system is working properly. I know we keep asking more ?'s, but.

Get all 4 wheels of the ground. Put it in 4lo. Is the front drive shaft out of the tranfer case rotating? If it is can you stop both front wheels from turning at the same time? Also try this in 4hi.

Really a wierd thing, but we'll try to get you fixed up. Have faith in us. (I hope).

ltljon · 09-13-2007, 09:33 PM

Quote:

Originally Posted by 777stickman

That is really wierd because it sound as though the 4wd system is working properly. I know we keep asking more ?'s, but.

Get all 4 wheels of the ground. Put it in 4lo. Is the front drive shaft out of the tranfer case rotating? If it is can you stop both front wheels from turning at the same time? Also try this in 4hi.

Really a wierd thing, but we'll try to get you fixed up. Have faith in us. (I hope).

I'm gonna try to catch the tire shop with an empty lift one morning & see what happens with all 4 off the ground. That'll be easier than doing it with only one jack & shoreing up the axles. I'll keep ya'll posted.
Thanks again.

777stickman · 09-14-2007, 11:51 AM

One more thing. Get a scanner on it that's capable of getting into the 4WD system. This is called the ATC (Automatic Transfer Case). The ATC system is self diagnosing and there may be DTC's stored that can help out also. As far as using the "AUTO 4WD" function I believe the vehicle has to reach a certain speed for that function to be active. The speed has to be sensed by both the rear and front speed sensors. If you select 4LO or 4HI speed sensing is not required.

Warning lights: "Service 4WD" in the dash indicates a problem with the front axle engagement. Blinking lights on the selector panel indicates problems with T-Case system.

ltljon · 09-18-2007, 06:11 PM

Update:
I jacked it up & crawled under truck while someone else put it in & out of all stages. When truck is in 2 hi (transmission in neautral) the front drive shaft will turn freely by hand. When any of the 4wd buttons are pushed I can hear & feel it engage in the transfer case & the drive shaft won't turn by hand (trans still in neautral). It is locking in you'd think but when I put it in drive or reverse while pressing the gas pedal the front drive shaft doesn't turn at all under any amount of power.
Is it possible that there are some type of clutches in the transfer case that are slipping? I still hear no unusual sounds even while spinning it by hand & everything seems snug, no slop when moving front shaft.

777stickman · 09-18-2007, 07:49 PM

Man, this is really getting weird!! Could it be a front diff problem? Obviously the backs are spinning but the fronts are not. So, with it in N and 4lo or 4hi and all four off the ground can you spin a front wheel while the other one is held or even can you spin one and the other goes in the opposite direction?

With this latest post I would take the front drive shaft off and do the same thing and see if the front output shaft is turning in the t-case.

I think we're getting close..........Steve

PS: Stay away from the "4wd Auto" for now.

silverado122775 · 09-19-2007, 09:56 AM

I think if it was the front diff, he would hear something, it may even prevent him from driving since the diff is used even when the truck is in 2wd.
this diffently sound like a t-case issue.

ltljon · 09-24-2007, 06:30 PM

I've been under the weather for a few days so haven't had a chance to tinker with it til today.
Here's what we did & granted it wasn't safe it served the purpose I think.
Jacked up the front end, front wheel spins freely while in 2wd. (as expected)
Locked in 4wd & by turning one front the other turns also in opposite direction. (as expected)
Front drive shaft never spins but moves just a frazzle each time you change direction of turning front tire. (not expected)
Put parking brake on & scotched rear wheels (the not safe part) & put truck in forward 4wd. By giving it just a little throttle the front would barely move like it wanted to turn but wouldn't. It would only "jump" like it was about to take off.
It's almost making less sense than before huh? It's still like theres something slipping in the transfer case but I've never been into one so not sure whats in there. Also why would the front shaft not spin while spinning the front wheels?
Reckon it's time to let someone take it apart & see?

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