Offroad Trailblazers and Envoys

My AWD isn't Working! (Rainer, Bravada and 9-7x)

Something not working right?

by therealsethallen » Sat Jan 16, 2016 8:02 pm

So the issue at hand; My 9-7x seems to have AWD grip when I'm doing above 25mph. But I only have RWD when I'm just starting off, even if the rear wheels spin. But there's no reaction happening. To test this, I stopped on moderately snowy unpaved hill. The rear wheels spun, and the fronts did not engage, I had to back down the hill onto dry pavement in order to get started. Now last week when I was changing my oil, I put it in drive on the lift, and the front wheels did spin, but the "Service 4WD" light came on, and went off with the next ignition cycle. Now, I figure the Transfer Case and it's associated hardware (Motor and TCCM) are okay since the front wheels had power. I'm thinking a wheel sensor perhaps, but I feel like that would set a code and my dash is clear. I'm beyond stumped about this, and for that matter I'm broke too. I'm really at my wits end with this, my mechanic says the front diff might be bad, but I've heard very few cases of front diff failure. I am unsure of the truck's service history before 90k miles.

Remember this is an NP4 Transfer case.
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by Jrgunn5150 » Sat Jan 16, 2016 10:08 pm

So do AWD vehicles still have disconnects?
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by therealsethallen » Sat Jan 16, 2016 10:35 pm

They do.
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by Jrgunn5150 » Sat Jan 16, 2016 11:36 pm

Well when my disconnect pooped, I had no code, I just got stuck in a mudhole spinning the back tires lol
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by therealsethallen » Sun Jan 17, 2016 12:31 am

I don't want it to be that, but to be honest with you what else could it be? Blue Meanies in my Transfer Case?
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by TBYODA » Sun Jan 17, 2016 2:55 am

What is the history on the transfer case and miles, have fluid changes been done every 50k. As far as the disconnect reach in on the inner cv a push up should be very little movement.
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by therealsethallen » Sun Jan 17, 2016 3:50 am

Was done at 92k. I'm at 132k at the moment.
It was done by a GM dealer before I bought the vehicle. It was serviced there pretty much its entire life. I have a meticulous service history for it (one of the major reasons I chose to buy it)
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by navigator » Sun Jan 17, 2016 8:44 am

His disconnect should have the awd sleeve. I think I would start somewhere else. Since it works sometimes, my guess would be whatever tells the awd to engage.
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by TBYODA » Sun Jan 17, 2016 3:13 pm

therealsethallen wrote:Was done at 92k. I'm at 132k at the moment.
It was done by a GM dealer before I bought the vehicle. It was serviced there pretty much its entire life. I have a meticulous service history for it (one of the major reasons I chose to buy it)


If you have not changed the fluid in the transfer case every 50k is possible most likely the clutches in the transfer case are worn out. IIRC in a AWD system there is no switch and normally from what I have read in AWD there is a 5% load up front all the time and adjust up higher % as the rear wheels slip. So if the clutches are worn out... You get the picture.
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by therealsethallen » Sun Jan 17, 2016 4:08 pm

I'm looking into replacement NVG126 cases now. Rebuilding is possible but I can't have my truck hogging up a lift. Found one for $200 with about the same millage pretty close to me. I'm not going to buy it without knowing they'll take it back if it's not my issue. But first, I'll try some fresh Auto-Trak II and see what that does. Fortunately I'm about due for an oil change anyways so I'll just do it then.
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by Jrgunn5150 » Mon Jan 18, 2016 12:12 am

navigator wrote:His disconnect should have the awd sleeve. I think I would start somewhere else. Since it works sometimes, my guess would be whatever tells the awd to engage.



So AWD trucks have a dummy disconnect? You'd think I'd know this since I have an AWD disconnect in my truck lol.
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by therealsethallen » Mon Jan 18, 2016 1:03 am

Jrgunn5150 wrote:
navigator wrote:His disconnect should have the awd sleeve. I think I would start somewhere else. Since it works sometimes, my guess would be whatever tells the awd to engage.



So AWD trucks have a dummy disconnect? You'd think I'd know this since I have an AWD disconnect in my truck lol.



It's some kind of wonderful. My goodness, two classic rock references in the same thread. I really don't know how the front works. All I know is my TC is probably shot.
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by v7guy » Mon Jan 18, 2016 1:12 pm

It could be the transfer case encoder motor too, not saying it's not the clutches, but it's another option.
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by bartonmd » Mon Jan 18, 2016 3:32 pm

The T-case encoder is the most likely thing to fail on an AWD (that otherwise seems to run fine, anyway), FWIW.

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by therealsethallen » Tue Jan 19, 2016 6:25 am

It's my understanding that all of GMs encoder motors from 1999-07 (The GMT800&360/70) had pretty high fail points. I got a really good offer on one. My local junkyard that I do gobs of business with offered me a TC from a Rainer for $200! With 66k on the clock. But they sold the shift motor off it already so I'd need to hunt one down. I'm going to do a TC fluid change with my next oil change first.
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by navigator » Tue Jan 19, 2016 8:32 am

If you have to swap TCs have you thout about getting one out of a TB so you can turn off awd all the time and have a low range? It would be more work but would be worth it if it were me.
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by therealsethallen » Tue Jan 19, 2016 12:44 pm

It's my understanding that all of GMs encoder motors from 1999-07 (The GMT800&360/70) had pretty high fail points. I got a really good offer on one. My local junkyard that I do gobs of business with offered me a TC from a Rainer for $200! With 66k on the clock. But they sold the shift motor off it already so I'd need to hunt one down. I'm going to do a TC fluid change with my next oil change first.
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by therealsethallen » Tue Jan 19, 2016 12:51 pm

navigator wrote:If you have to swap TCs have you thout about getting one out of a TB so you can turn off awd all the time and have a low range? It would be more work but would be worth it if it were me.


I've played with the idea, but I don't want to deal with the wiring, I'm not a serious off roader and the height I'm at now seems to be perfectly acceptable and the all wheel drive is fine. I'm going to get a set of 17" spare rims and put some kind of aggressive tire on them for next winter
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by KingBird » Sat Jun 25, 2016 11:45 pm

When I still had the 126 in my Bravada, I had to change encoder motors every three to four months. I got to the point that I always had a known good encoder motor in the rear floorboard, when I had to change mine, I'd take the old one to O'Reilly's and get a warranty replacement.

Since I installed the 226 case and rewired the vehicle to work with it (it thinks it's a TB), I haven't had any trouble with my encoder motor which is the one that was on the TC when I got it from the junkyard. I still have a spare though...
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