2002 Oldmobile Bravada Smart Trac Help!!!

I bought a used Oldmobile Bravada on Friday and have noticed a tightness when I turn. I really am having a hard time describing it. It feels like it is in 4 low. I have changed the transfer case fluid. The AWD is working I am just not sure if it is disengaging. I am in the process of trouble shooting this issue. I have owned many four wheel drive suv's just not ones with the Smart Trac system. I have read all of the forums posted and was wondering if anyone has new imput with this topic. It is an awesome car!! Just very confused!! :banghead:

GM has a new fluid for the Smart Trac system, it's blue in color and is supposed to take care of the issue you're experiencing. Sometimes requires changing the fluid again after 100 miles.

Thanks I was told by a Trans shop that the clutches inside the transfer case may be binded together.. Is this possible? Also is there a way I could trouble shoot this and see if maybe it could be the ATC or something a little more affordable..I bought this SUV on a snowy day so I was unable to feel this binding on the test drive.

On the new body style 2002 Bravadas it almost always the encoder motor that has failed. There is a bulletin out:
#02-04-21-008A: Shudder, Rocking Motion, Binding, Feels Like Vehicle is Stuck in 4WD (Crow Hop) When Turning at Low Speeds (Replace Transfer Case Encoder sensor and Reprogram TCCM)
It describes changing the t-case fluid, replacing the sensor, and reprogramming the T-case module. My experience has shown its better to replace the whole encoder motor and not just the sensor.

On the new body style 2002 Bravadas it almost always the encoder motor that has failed. There is a bulletin out:
#02-04-21-008A: Shudder, Rocking Motion, Binding, Feels Like Vehicle is Stuck in 4WD (Crow Hop) When Turning at Low Speeds (Replace Transfer Case Encoder sensor and Reprogram TCCM)
It describes changing the t-case fluid, replacing the sensor, and reprogramming the T-case module. My experience has shown its better to replace the whole encoder motor and not just the sensor.
I have a 2001 Bravada that I purchased about 6 months ago. Pretty sure this is the same thing I have experienced. Actually, I thought at times like when pulling into a parking space, that I had lost the power steering. Mechanics have blown me off as a female driver who doesn't know what I'm talking about. Do you think this is the same as what you are talking about here?

Yes, sounds like the same thing.

I took the Bravada back to the dealer I bought it from and he returned my check and took the car back. I took in an estimate to fix the Bravada and it was in the thousands. The clutches in the transfer case were completely welded together. The mechanic said it was so bad that it was impossible that the dealer was unaware of the problem. I loved the SUV but was fearful that it was going to be a cronic problem. When I test drove the car it was snowing outside and I was under the impression that the AWD was activated because of that. Should have thought differently. I was told by the trans man that most of the time the TCCM goes bad and people neglect to fix it, in result the damage to the transfer case is great and will be very costly.
Great SUV bad AWD design...proceed with caution when purchasing a GM with the Smart Trac system!!!:uhoh:

The mechanic said it was so bad that it was impossible that the dealer was unaware of the problem....
I was told by the trans man that most of the time the TCCM goes bad and people neglect to fix it, in result the damage to the transfer case is great and will be very costly.
Great SUV bad AWD design...proceed with caution when purchasing a GM with the Smart Trac system!!!:uhoh:

Believe what you want to believe but honestly the clutches welding together isn't really possible.
I've never seen a TCCM fail and I work in a large (former) Olds dealership.
Although I personally don't care for the Bravada AWD, I don't believe its a bad design.

I have a 2001 Bravada that I purchased about 6 months ago. Pretty sure this is the same thing I have experienced. Actually, I thought at times like when pulling into a parking space, that I had lost the power steering. Mechanics have blown me off as a female driver who doesn't know what I'm talking about. Do you think this is the same as what you are talking about here?

Well not exactly, the 2001 is slightly different. The usual fix for crow hop in those is double t/case drain and refill (with the blue Autotrak GM fluid) with a 5 mile road test in between. Sometimes other things fail like the encoder motor or the clutches. But usually 90% are fixed with the double drain and refill. Ask the GM dealer to do a bulletin search and follow the service bulletin.

I have a 2000 bravada and I also is stuck in 4X4 mode -- I am not sure on a encoder motor / sensor on this year -- Is there one and How do I test it? I have changed my transfercase fluid out twice and it did help for a few days but I gave up on it since it does not last. I was just at Advanced Auto parts store today and they now sell the GM Fluid -- It is some Pennzoil brand. FYI

If the fluid change helps then you most likely don't have a problem with the encoder motor. Most like the clutches don't have enough clearance, either because of dirt/grime build-up or I also seen chunks of silcone sealer (used to seal the halves of the case together) in between the clutches. If that the case then its best to dissassemble the t/case, clean or replace the clutches and re-shim the clutch clearance. The factory set them up tighter then we do now.

Thanks for the info 83 !!!--- I am thinking about doing a triple gear oil change in like a 3 week period and if that dont work then I will drop the transfercase. And go with your idea. I have been searching for ideas for this problem for over a year. If I do a transfer case overhaul then I will post a new thread for spec's on what are the clutch clearance's -- My haynes manual does not go that far in depth. Hopefully you or someone will be able to help me then. Again thanks for the info

That fluid change helped for a couple days. The former owner of the Olds let this problem persist for such a long time that it damaged the clutches in the transfer case. The dealer changed all the equipment that was listed. They reprogramed the computer and still the problem persisted. I even went as far as to check the tire size and pressure. Quite honestly I am limited in knowledge with trans equipment. Thanks for all your advice I hope that all is well. I ended up picking of a mint conditon 98 dodge ram.


Thanks for the info 83 !!!--- I am thinking about doing a triple gear oil change in like a 3 week period and if that dont work then I will drop the transfercase. And go with your idea. I have been searching for ideas for this problem for over a year. If I do a transfer case overhaul then I will post a new thread for spec's on what are the clutch clearance's -- My haynes manual does not go that far in depth. Hopefully you or someone will be able to help me then. Again thanks for the info

thanks for your response Tmenna -- This is making me think that your vehicle problem was something other then the transfercase. Possibly mine could be the same thing. I changed the right front wheel bearing a month ago becouse of a loud noise coming from that area. After I changed the bearing the noise was gone and I was hoping at the time that wheel sensor was bad and was causing my transfer case problems. But it did not change anything other then the noise went away. Could my left side wheel bearing be bad and sensor not working and me not even notice it -- and if that is a yes -- would that have something to do with my transfercase being in 4x4?

83Cutlass - Finally someone who has seen the inside of one of these things and dealership experience! I like what I am hearing!

I have got to say this has been my suspicion for some time.. That there is excessive drag common in this clutch pack setup..

I have a 2000 and the previous owner was given the run around by repair shops who really did not know what to do. so that it hopped and clicked like mad in a tight full stop when I test drove it.

I did fluid changes and that helped but there is still noticable drag anytime that the wheel are turned tightly. I suspect that my MPG is suffering somewhat as you really never feel that it is in 2WD. I do not know what the smart trac felt like new? should it feel like any other 2WD system when not engaged?

Before I do anything to the transfer case.. I would like to test the transfer case motor to see if it is part of the problem. Can I just test this off the vehicle with 12V? There is a warning about doing this - What is the concern?

Also I assume that the motor applies pressure to the clutch pack? to engage the transferr case? Can i manually check that the motor is retracting all the way? If so what is the disengaged position? Is there a measurement or a clock position?

Thanks,
Matt

Yes you can bench test it with a 12 volt power and ground source with no worries. It just spins back and forth to swing a fork inside the t/case to apply the clutchs. Can't exactly remember the disengaged orientation but you should be able to tell with the motor off by gripping the stub shaft on the t/case with a pliers and moving it. It'll kinda spring back into the disengaged position. Set you encoder motor back that way B4 reinstalling it.
You bravada won't feel exactly like a 2wd when you out driving around. A 4wd Blazer in 2wd mode feels peppier the the AWD Bravada IMHO.

On the new body style 2002 Bravadas it almost always the encoder motor that has failed. There is a bulletin out:
#02-04-21-008A: Shudder, Rocking Motion, Binding, Feels Like Vehicle is Stuck in 4WD (Crow Hop) When Turning at Low Speeds (Replace Transfer Case Encoder sensor and Reprogram TCCM)
It describes changing the t-case fluid, replacing the sensor, and reprogramming the T-case module. My experience has shown its better to replace the whole encoder motor and not just the sensor.

Hi.
1st, thank you for all your help and info on this site!!
I have an '02 with only 26K that started doing what you described above early this year? My ? is can I get away with just changing the encoder motor and fluid change or do I need to have the TCCM reprogrammed as well? I suspect reprogramming is a dealer only job???
Thanks again,
jjg14080

Well yes you can but I'm not sure if there will be any consequences. The updated calibration is a dealership only thing. The new calibration is described as improved Transfer Case Operation In AWD Mode, but I'm not exactly sure what they changed.

I have a 2002 Bravada as well. As I would be backing up, start going around a corner, etc it would make a clunk and engage, feeling like it was stuck in 4wd. I was told it was the transfer case issue and the fix was simply drain the transfer case twice with the 5+ miles between because everything after 2001 had a purely hydraulic system with no encoder, etc. Apparently that was incorrect information about the encoder.

The flush twice didn't help and now something has broken. At first guess it seemed like the front left axle had broken, but it appears to be intact upon raising it up and looking underneath. I can however take this wheel and spin it probably 15-20 degrees back and forth before it engages anything. Once you get to that point you can see that rear driveshaft begins to turn.

I'm expecting I need to actually replace the transfer case now. I don't have a lot of money right now though. GM wanted $1800 for the transfer case alone! I see a bunch of transfer cases listed for 2003-2004 Bravada on ebay, but I don't see any listed for 2002. Was there something specifically different about the 2002? Looking at GM PArts direct I see 4 models for the transfer case and different years for each:

model 126c, bravada/envoy/trailblazer, 113" wheelbase 02-07
model 226c, bravada/envoy/trailblazer 02-07
model 233c 02-04
model 236 02-03

How do I know which one I have and which one I need to get? Or is it possible that this issue is a front differential issue that is different from the transfer case issue? Any help is appreciated.

John

I have a 2002 Bravada with only 38K miles, have always had the issue with tight turns: heavy vibration or "crow hopping" as GM calls it. Not a single dealership/repair place has ever fixed it. The steering has been lubed and the transfer case fluid was replaced recently twice, the problem gets better and stays fine for about 200 miles, then it goes back to the heavy vibration. We've lived with this for years, but recently we noticed a vibration in our driving in lower gears and reverse, without turning but straight ahead driving. The vibrations could be felt through the pedals and the floorboards under the driver and passenger feet. We took it in to a dealership here (just moved, don't know any good mechanics) and they kept it for 5 days and were stumped, so they contacted Chevy/GM and they told them to make sure the tires were up to spec and to put on new tires to see if that would stop the vibration, it didn't. Then they said it was the encoder motor, so the shop replaced that, and it didn't help. Finally they simply changed out the transfer case fluid twice. That got rid of the binding during tight turns but not the vibration we are feeling at low gear. They said to just take it home and see how it drives for the next 500 miles or so. That's what we've been doing, and at 250 miles the heavy vibration is starting to come back during tight turns and the vibration in low gears straight driving is getting worse. I'm going to take it in again next week to have them look at it.
Also, I have heard a rumor that due to powertrain issues, GM had put a 7 year/70,000 mile warranty on the powertrain. Does anyone know if that is true? If so, we still qualify and that would be a huge relief!

I don't think there is any extended warrenty offered by GM for this.

Here's a pretty complete rundown of how to diagnose a t-case crow hop.

#PIP3928A: Bind Or Shudder On Turns (Crow Hop) - keywords auto AWD chatter vibration - (Dec 18, 2006)


Subject:Bind or Shudder on Turns (Crow Hop)

Models:2004-2007 Buick Rainier
2002-2007 Chevrolet Trailblazer
2002-2007 GMC Envoy
2002-2004 Oldsmobile Bravada
2005-2007 Saab 9-7X

For the 2002-2003 Bravada or the Envoy and Trailblazer (in auto mode only) please reference the latest version of tsb 02-04-21-008. If the tsb has already been performed or the vehicle falls after the tsb use the below diagnostics to isolate an electrical or mechanical concern.

Disconnect the encoder motor electrical connector. If the condition is gone, then proceed to step 2. If the condition is unchanged, then skip to step 4.
Reconnect the encoder motor connector and swap the wheels and tires from an identically built vehicle that does not exhibit the concern and re-evaluate the condition.
If disconnecting the encoder motor connector corrects the condition and swapping tires from another identically built vehicle does not improve the concern, snap shot the TCCM data and monitor the prop shaft speed sensors for spikes or dropping out.
For Bravada Rainier and 9-7X remove the encoder motor and evaluate if the concern is gone replace the encoder motor. For the Trailblazer and Envoy remove the encoder motor and with the tech 2 in powertrain, select "Special Functions", next select "ATC Output Controls", next select "Engage Front Axle". From this screen lock the front axle and evaluate. If the concern is gone replace the encoder motor.
If none of the above change the condition, remove the front prop shaft and evaluate. If the concern is gone suspect a possible internal transfer case concern. If the concern is still present with the prop shaft removed suspect either a locking differential or steering related concern.

There has also been a problem with encoder motors recently. They keep burning up fast. You may go through a few before you get a good one.

Thanks 83,

I took my Bravada back in after driving it for another 700 miles with no change in the condition. Started hearing a worse vibration when the car was in reverse. Today, they told me that they fixed the vibration I was feeling during normal low speed straight-line driving. Apparently some hosing for the power steering was out of place, sure enough that vibration is gone. They tell me I DO need a new encoder motor to get rid of the "crow hop" during tight turning, that's cost $1200.
Then they hit me with something else: the right front axle is loose. They tell me that when they put it up on the hoist, they can move the wheel up and down with way too much ease. They have two solutions for me: go in and change the wheel bearing because a bad bearing might be causing this problem, but they aren't positive. That'll cost $1125 parts and labor. Or, worse, take apart the whole front differential and see what else could be causing the problem, because there are metal shavings found in fluid (?) which they say is leaking around the CV boot. This will cost $1400 just for labor. They can't give me a firm quote yet because they don't know what's wrong, so no diagnosis. They did say up near $2000 though. So, does this sound reasonable? Am I being played, because now that the vibration that I originally took it in for is gone, I can feel nothing wrong with the car (not that that means anything). I think I'm going to take it in for a second opinion tomorrow. Also, this car only has 38K miles on it, isn't that kind of early for a problem such as this? Not only that, I've already had to change out the front suspension (around 20K miles). How problematic are these vehicles?

Thanks for any help, I'm getting really frustrated and going broke!

ok, an encoder motor by itself costs between $500 and $600 plus labor of 1.1 hours(depending on which labor time guide is used) is about $110 ($100 per hour shop rate). So thats $710 plus the T/case module updated reprogram ($70), the T/case drain and refill, and diagnosis could get you near $1200ish.

As for the other problem, if they can move the wheel up and down, then that is a bad wheel bearing. If they can move the RF axle up and down at the inner end then its the intermediate axle shaft bearing assembly. A wheel bearing does not cost $1125. Should be like $400 parts and $150 labor at $100/hour for a TOTAL of $550ish

Metal shavings in the front axle is lube is concerning but can be somewhat normal. If you don't hear any bearing or gear noise from the front axle then there is no reason to go into it and fix it. Especially on one of these because it is extremely time consuming($$$) to remove the axle assembly.

Whats leaking around the CV boot, diff fluid or CV axle grease. I'm guessing diff fluid from your description. You might wanna fix that eventually.

ok, an encoder motor by itself costs between $500 and $600 plus labor of 1.1 hours(depending on which labor time guide is used) is about $110 ($100 per hour shop rate). So thats $710 plus the T/case module updated reprogram ($70), the T/case drain and refill, and diagnosis could get you near $1200ish.

As for the other problem, if they can move the wheel up and down, then that is a bad wheel bearing. If they can move the RF axle up and down at the inner end then its the intermediate axle shaft bearing assembly. A wheel bearing does not cost $1125. Should be like $400 parts and $150 labor at $100/hour for a TOTAL of $550ish

Metal shavings in the front axle is lube is concerning but can be somewhat normal. If you don't hear any bearing or gear noise from the front axle then there is no reason to go into it and fix it. Especially on one of these because it is extremely time consuming($$$) to remove the axle assembly.

Whats leaking around the CV boot, diff fluid or CV axle grease. I'm guessing diff fluid from your description. You might wanna fix that eventually.

Thanks again, I took it in for a second opinion to a Midas near me and the tech had it up on the hoist for 30 seconds, came back and said there was leakage around the CV boot and that there was almost no fluid left. They quoted me $385 for labor and parts to replace the whole CV assembly. I went ahead and did that. Will take it back in to a place that I have been told is reputable for a checkup in a month or so (assuming nothing goes wrong). So, just a recap: the dealership did fix the vibration that I originally took it in for, simply moving hoses around from the power steering, and they changed out the transfer case fluid twice and the "crow hop" has not returned (much). Midas fixed the CV boot leak/replaced the whole unit.
I guess my problem here is that I never felt anything wrong with the axle/CV boot to begin with so I don't know how I'll know there's a problem again until it's too late.
Thanks again 83.

For the second time in less than 3 years I have replaced the encoder motor to fix the grabbing problem. The first time was under warranty, this time I was $850 lighter in the wallet after the repair.

After taking the problem and potential fix of replacing the encoder motor(learned on this forum) to my regular mechanic, he wanted to see if anything else was causing the problem (presumably so he could save me a few bucks, but who knows). That was great but 3 visits later (at no charge) I still had the issue. So over I went to a Chevy dealer close to my work, where the repair was completed.

They originally thought it was the sensor only, but after replacing that and getting the vehicle back together, they figured out it was the motor too.

Obviously it is very frustrating this part, which ain't cheap, does not seem to last very long. JC Whitney advertises a less expensive after market part
(http://www.jcwhitney.com/autoparts/ItemBrowse/c-10101/s-10101/p-100000447293/mediaCode-ZX/appId-11433748/Pr-p_CATENTRY_ID:10000044729311433748), I don't know if it includes the sensor, etc. If anyone has tried this part, it would be great to hear some feedback.

Good luck.

Good day,
I was having some problems with crow hop so I took it to the dealer who told me that it was my Encoder Motor and that it would cost me 1500 to have it replaced not to mention 250 for the diagnostic. I have read that if I take the 4x4 fuse out that it could fix the problem which it did for two weeks. Now my trouble light is on permanently and I am getting crow hop like you wouldn't believe. Can anyone tell me if there is a way to disengage the 4x4 without the use of tools? This is just a temporary thing while I wait for my $200 part from ebay to show up.

Thanks in advance.

Sebastian

Well my part came in and everything went great to replace the encoder motor but now I found a\the bigger problem...Something went loose in the transfer case made a hole in the top of the transfer case and is lodged in the side of the hole... Great diagnostic dealer... Oh well found a new one for 800 going to install it tonight...

Is this a regular occurance with the NP4 Transfer Case or am I just special???

I have a 2001 Bravada and it does the shudder thing after I'm going at a higher rate of speed. I doesn't do it when I'm in mud or snow turning going slow, only on concrete after I've been going down the road 45 or faster. Would this be the same thing y'all are talking about? Being an offroad enthusiast I know the shuddering isn't good for T-case or tranny. But, the AWD SmarTrac fun freakin' computer crap confuses the heck outta me. Also, I've heard that a cheap fix for this is to take the T-case drive shaft out. Not really hard I don't imagine as I've taken plenty of driveshafts out on both 2 and 4-wheel-drive. Has anybody done this before? Any help with it would be much appreciated. Thanks.

I had awd stick in my bravada a year ago. It ended up being a stuck encoder motor. I hope this helps.

Thanks for the info, did you change the transfer case lube to the Autotrak II blue fluid also?

I purchased a 2002 Bravada in April of this year, and got in trouble the first time I drove it due to taking a corner to fast. I lost control and tangled with a road sign. Not much damage but I learned to slow down. What I don't understand is when I get on ice or slippery roads I can feel the rear tires break free for an instant then nothing more. I've never gotten stuck, even in this specially harsh winter we had in Northwestern Ohio this winter. I don't know anything about AWD or SMART TRAC !!, as I've always had rear drive only. As for some of you have said the fuel economy isn't all that great, thats true for around town/stop and go driving or driving over 65 mph. But, for me I didn't purchase it for gas mileage, but for towing and winter driving. Currently I am getting 12-14 miles per gallon around town and 28-30 miles per gallon at 60-65 miles an hour on the highway which really isn't to awfully bad.

Welcome to the site crafty61120152.
Congrats on your recent Bravada purchase. Your highway fuel mileage is certainly impressive.
You can do a search on "encoder motor" to get up quick on your model AWD.