No 4x4, but no indications of problems

Shdwdrgn

Original poster
Member
Dec 4, 2011
568
A bit different than the other threads I read, so I thought I would start a new one. Sitting in my garage, I flip the switch to 4hi, I can hear the normal sounds of the transfer case engaging. The indicator light shows it is in 4hi within a couple seconds, as expected. However it is definitely NOT engaging the front wheels. No binding from sharp turns, and on the snow this morning I had no problems breaking the back wheels free in the parking lot. So, anything jump out as a possible cause?
 

Wahugg

Member
Dec 4, 2011
87
View attachment 18408
Credited to OffRoadtb.com

Go through that list and let us know where the problems arise.
The roadie should be along soon enough to help you out. The 4x4 system is his favorite system. Other things you should keep in mind is how many miles are you at? Your TC fluid should be changed out AT LEAST every 50k.

Hope this helps
-Wahugg
 

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Shdwdrgn

Original poster
Member
Dec 4, 2011
568
I'm just about up to 80k. I bough it at 63k and the dealership insisted they had done all the factory maintenance. Of course I believed them. Oh wait, no I didn't. I just replaced the TC fluid (using the GM oil) and both axles (amsoil full synthetic) back in September. I didn't see anything wrong with the quality of TC fluid I drained out, and the 4x4 was working earlier this season.

I was in a minor wreck this morning, however, so the troubleshooting will have to come as I have time. Trying to get the radiator out of the fan so I can drive it again. Thanks for the chart though, that'll go a long ways!
 

The_Roadie

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Member
Nov 19, 2011
9,957
Portland, OR
Good luck on the fan repair. Statistically, the problem is most likely to be in the passenger side splined disconnect. They were poorly designed to be lifetime greased, and it doesn't always last. Run the troubleshooting flowchart, but also read this first from our sister site so you know the theory of operation.

Offroadtb.com Front Axle 4WD Disconnect
 

Shdwdrgn

Original poster
Member
Dec 4, 2011
568
Ugh... the spline repair looks to be all sorts of fun (depending on your definition of 'fun'). Well, fan repair first, then work on the 4x4, and finish up with the rock sliders (because what's the point of rock sliders without 4x4?) I should be able to finish that all up this weekend, right? :rotfl:
 

The_Roadie

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Nov 19, 2011
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Portland, OR
Shdwdrgn said:
... what's the point of rock sliders without 4x4?...
Rock sliders are indeed the sort of mod you never see on mall cruisers. Totally functional sort of thing that is hidden for the most part, recognizable almost exclusively by folks who know what they're good for. :wink:
 

Shdwdrgn

Original poster
Member
Dec 4, 2011
568
Well now here's an interesting development... After finishing repairs on the front-end today, I had to raise the rear wheels off the ground to verify I didn't bend a wheel. When I put it in drive, the rear wheels wouldn't spin. Turns out I was still in 4hi and the front wheels were getting the power. Afterwards, I drive it around a bit and confirmed that I am indeed getting 4WD wheel-hopping when trying to make a tight turn. Another test was parking with my front wheels on the dry driveway, and my rear wheels on the packed snow in the street. In 2wd and light braking, the rear wheels easily spin on the snow. In 4wd, the front wheels appeared to pull me forward and the rear wheels did not spin. (For reference, I do have a G80).

So now I'm really confused. Yesterday in 4hi there was no front wheel hopping in the parking lot, and I could easily fishtail the back end. I park in a connected garage, so the truck was not terribly cold. It simply did not feel like the front wheels were engaged. Of course there was also a foot of snow on the roads yesterday, and no solid pavement to be found anywhere, but I would think I would still feel the wheel-hopping when I tried making a fully-rotated turn.

Tomorrow I should have time to get the front end up on jacks and run through the flow-chart above, just to verify that the front wheels are in fact engaging. But if the 4WD is working today, are there any issues that could cause intermittent failures without throwing any dash warnings?
 

The_Roadie

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Member
Nov 19, 2011
9,957
Portland, OR
The splined disconnect can have all sorts of internal mechanical failures mostly involving the fork and the collar, and not have any indication electrically of the failure (flashing lights, etc.). That's because the electronic feedback is in the front axle actuator, and if its motor succeeds in pushing out the actuator button, the sensor reports success. But the actuator button has an internal spring so a mechanically jammed disconnect will not break the actuator, so what happens is the spring compresses, the disconnect is mechanically inoperable, but the actuator still reports success to the TCCM.

Cold, congealed grease inside the disconnect can slow down the actuator's success, and sometimes cause intermittent electrical failure reports.

The reason torque can go to the front wheels and the rears don't spin is because the transfer case clutches are like a front-to-back locker. The front and rear driveshafts are going to spin at the same speed, whether that's fast or slow. If all four tires are slipping, they pretty much slip together.

[video=youtube;AheKwL2AYhE]http://www.youtube.com/watch?v=AheKwL2AYhE[/video]

If you're on lumpy trails, with only two wheels having traction, then you need to have a G80 to have any hope of forward motion.

Looking closely at this old video of mine shows when the G80 kicks in, even a spinning FRONT tire slows down.

[video=youtube;24SwmSN0-bI]http://www.youtube.com/watch?v=24SwmSN0-bI[/video]
 

Shdwdrgn

Original poster
Member
Dec 4, 2011
568
So you're saying the (apparently) intermittent operation could possibly be a sign that the disconnect hasn't failed yet, but probably should be checked soon? Looking at the temperature, we were at about 28F yesterday, and around 36F today - although I would assume temperature is not really a factor since the mechanical components would heat up during operation anyway. I suppose that regardless, it would be beneficial to actually go through the steps and at the very least, get some good quality synthetic grease inside the disconnect unit before it *does* completely fail.
 

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