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AWD doesn't engage! Any clues, pretty pls??

3K views 18 replies 11 participants last post by  karls 
#1 ·
Holy crap, finally took my newish to me 2001 rig into the bush to tackle a bit of snow, ice, mud. The new tires rip, the chains helped but I was stunned to learn my front wheels do.....NOTHING :x Got stuck three times, crawled out with chains and shovel, just steeper pitches of gravel road caked in ice and some snow.

Had both rear wheels spinning yet no engagement at the front, I checked both sides (I expect only one front wheel actually drives?). I mean, when's the good time for the fronts to kick in if not when both rears are spewing gravel and ice?? :doh:

Anyway, can't find any threads on this except perhaps
viewtopic.php?f=70&t=10066
which speaks to the motor.

I have no AWD light on but lights briefly on start up so it works (I am guessing). No codes, had them checked last time in....then all the fluids changed and flushed too, paid a fortune for the best/required stuff (it was a lot more than $10 a quart as in other threads, I forget but man that was a little rich for a little fluid...), incl T-case, tranny, front and rear, tranny cooler added......suppose there could be a new code since last week...I will check the fuse that was mentioned. I DID recently change to crappy Chevy rims that fit great but were not stock and switched to 235/75 R15's. ABS seems to work most of the time, if not all the time I expect it to.

BUT: I pulled from a stoplight on a rainy road the other day and the fronts DID engage, making the vehicle churn on in not the most comfortable feeling fashion tho bouncing around....also I have felt the fronts do a 4x4 lurch I have noted in my 4x4 suburban in the past....so I am stunned the F*&%er doesn't work....except I used a few other words when stuck in the bush. Any ideas?? thanks all
:feedback:
 
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#2 ·
grrrr blown ATC fuse under the hood....now the question is ....why? (apart from why didn't I friggen check it when stuck on the hill but that's another question with a different answer... :oops: at the time I was slidding backwards downhill ....and when I finally stopped just beside a creek bank I was a little flustered)
 
#3 ·
Glad we could help :lol: at least you know what, now maybe someone can shed light on why.

I love my AWD, when I feel the fronts power up I'm on it even more. It's perfect for the rainy weather here, I don't have to wait for a big gap in traffic to pull out, just mash and go :layrubber: Freaks people out sometimes, but then I'm up to speed quicker then anything other then a Subaru or Audi :mrgreen:
 
#4 ·
So, not to hijack your thread or anything, but the 99+ AWD vans have an automatic transfer case? Is it like auto 4x4 in other vehicles? In my 97, I'm pretty sure that all 4 wheels are powered all the time, no matter what. Is an automatic transfer case more fuel efficient?

As for the fuse, I can't imagine what in there would make it blow. You could have a short somewhere else or it could be a one time thing. If you replaced the fuse and it doesn't blow again, it's probably okay. If it does, I'd start by looking for chaffed wires.
 
#5 ·
Yes, the 99+ vans have a NP136, which is the 4-hi only version of the NP236 used in Blazers, etc. It only engages when it detects slip; otherwise, you're RWD.

The 98 and down vans have a BW4472 t-case, which is a mechanical, 65% rear, 35% front full-time AWD case.

Supposedly, the automatic t-case makes you a little more fuel efficient, but I really don't see any difference between my '93 Bravada and '99 Safari.

My fuse was blown when I bought my Safari. When I couldn't get it up on 4 ramps, I replaced the fuse and got it up on the ramps. It's never blown since. I figure the PO just did something stupid and blew it.
 
#7 ·
strangerock said:
In my 98 I just sold I was getting 19 mpg , replaced it with a 2002 and I am getting 16.8 mpg......

StRaNgErOcK
That could be due to laggy O2 sensors...they don't set a hard code. Just figured that might help...my wifes Explorer dropped mileage a bit and I did a scan and found a slow 02 sensor code for the passenger side...you can't really detect any driveability issues with it, but the mileage certainly suffered. We were getting 20mpg pure highway and the following trip along the same route netted us 16mpg. I thought it might be the Air filter as it was dirty, but now I suspect that O2 sensor...it's getting replaced ASAP.
 
#9 ·
Leeann_93 said:
Yes, the 99+ vans have a NP136, which is the 4-hi only version of the NP236 used in Blazers, etc. It only engages when it detects slip; otherwise, you're RWD.
The 98 and down vans have a BW4472 t-case, which is a mechanical, 65% rear, 35% front full-time AWD case.
Supposedly, the automatic t-case makes you a little more fuel efficient, but I really don't see any difference between my '93 Bravada and '99 Safari.
My fuse was blown when I bought my Safari. When I couldn't get it up on 4 ramps, I replaced the fuse and got it up on the ramps. It's never blown since. I figure the PO just did something stupid and blew it.
redfury said:
Oh, and I've got a pushbutton 4x4 in my van...taken out of a Blazer. It's nice having 2wd, and 4lo and 4hi at the push of a button.
Thanks much for that input, I have no idea about that and this is great to consider. I may in future update the Tcase to have low/hi or just run it in 2wd.
Just an update: the fuse has not blown again since and now I cannot with certainty say that the "service AWD" light was ever on upon start up (think I recall the ABS instead) since I got it but did have the sense the thing WAS working. If not, perhaps Karma took care of the guy trying to stick me with a 2wd AWD :naughty: wondered why he was letting it go so easy but it had many other issues I have since fixed :!:

As for mileage, not too great but no nasty surprise either, getting 16.4L/100km (17mpg imperial) with old tires, with the larger ones (which must affect speedo by minus 4%) gets now 16.9L/km. No codes for O2 sensor, but that's good to know they may not set hard codes... Thanks all for the great info, much appreciated, really :cool:
 
#10 ·
I hear you on the fuse. I bought a 97 Dakota ( previous to the van ) and it ran like crap. Got it cheap. Drove it home and started looking around and found the 10amp fuse for the computer to be blown. Replaced the fuse and whaddya know? :D
 
#11 ·
Update: no problems since, the front wheels pull like a SOB :cool: and are back to scrubbing my new tires off in tight turns :roll: but my gas mileage is down a full 1.5L/100k (I think that may answer some of the related questions in the MPG thread) so in summer I may just install a switch to turn the AWD off on longer highway trips :!:
 
#13 ·
I have a problem on my 98 AWD. The Tcase is engaged front drive shaft is turning (On Jack Stands) but front wheels aren't turning. It drives fine but lacks a bit of power and no unusual noises from the front. I've hit a wall here :banghead: .
 
#15 ·
yeah, gear/shaft failure inside would have been my guess....no noise tho...maybe the diff has been cleaned out by the last owner :? can ya ask? I have a LOT of questions for the last owner who sold me my lemon....but I'm gonna let Karma take care of it :evil:
 
#16 ·
kus said:
Update: no problems since, the front wheels pull like a SOB :cool: and are back to scrubbing my new tires off in tight turns :roll: but my gas mileage is down a full 1.5L/100k (I think that may answer some of the related questions in the MPG thread) so in summer I may just install a switch to turn the AWD off on longer highway trips :!:
I wonder if some of that mileage decrease is the lift and tires?
 
#18 ·
Corsemoto said:
kus said:
Update: no problems since, the front wheels pull like a SOB :cool: and are back to scrubbing my new tires off in tight turns :roll: but my gas mileage is down a full 1.5L/100k (I think that may answer some of the related questions in the MPG thread) so in summer I may just install a switch to turn the AWD off on longer highway trips :!:
I wonder if some of that mileage decrease is the lift and tires?
no, don't think so, tho I suppose it can be a number of things....driving more aggressively, O2 sensors etc.. but had several fill ups and calcs prior to doing the tires, always the same mileage and then even after the lift, all the data shows fuel use increase after the AWD was "fixed"...I do not mind tho, sooooo much better/safer driving in the rain/snow. I don't think I EVER want another non-AWD the difference is so significant.....but then I drive a lot in (rain) storms due to my windsurfing/wave sailing hobby so I really notice and appreciate it. :!:
 
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