1998 olds Bravada Encoder Motor/Transfer Case Problems. Help?

redddogg60 · #1 01-17-2008, 07:54 PM

I recently had my encoder motor replaced by a local mechanic(after market). Now the vehicle is in All-wheel drive all the time. I've tried pulling ATC (automatic transfer case) fuse. That didn't help. After reading other posts... I was going to have transfer case fluid replaced with GM's synthetic fluid. My owners manual calls for dextron-mercon III. Should I still try GM's synthetic (as mentioned in other posts) or use dextron III??? What is the next step in trouble shooting this problem??? Thanks in advance for any help you may offer!!!!

Chris Stewart · #2 01-18-2008, 04:57 PM

Best results have been reported by members using the GM AutotracII blue fluid.

redddogg60 · #3 01-18-2008, 05:17 PM

Quote:

Originally Posted by Chris Stewart

Best results have been reported by members using the GM AutotracII blue fluid.

Thank you. I will try the AutotracII blue. Helpfully this will cure my problem.

redddogg60 · #4 01-22-2008, 11:09 AM

Quote:

Originally Posted by redddogg60

Thank you. I will try the AutotracII blue. Helpfully this will cure my problem.

I changed my fluid twice but the vehicle is still stuck in all-wheel drive. It is especially bothersome when turning tight corners as metioned in other posts. What is the next step in troubleshooting this issue. Thanks.

Chris Stewart · #5 01-22-2008, 07:55 PM

It's been mentioned that it takes a few hundred miles to loosen the transfer case innards after the lube change.

Removing the front driveshaft will stop the binding but it also makes it 2WD.
You might make sure all your tires are the same size and you have 32psi in the front tires and 30psi in the rear tires. The most weight is over the front tires hence the higher air pressure to try to maintain the same tire diameter on all 4 tires.
I guess it's possible the encoder motor might've been installed in the wrong position...all help gratefully accepted.

redddogg60 · #6 01-22-2008, 10:12 PM

I will drive it for a week or two, then change the fluid a third time. I will make sure tire pressure is within mentioned specs. If that doesn't work I will pull encoder motor. Thanks for checkin' in with me. May I mention to others with a '98 bravada... when changing fluid in the transfer case, the 1/4" filler and drain plugs are made of aluminum. Be gentle with them and you'll be O.K.. Also, buy a manual fluid pump (bought mine at Harbour Freight for $6) it looks like an overgrown soap pump. It made this job a breeze. I'll keep you posted with my progress or lack of.

matt_o_70 · #7 01-27-2008, 06:19 PM

what was the original reason to change the encoder motor? Seems that if this was only a problem after the repair - then something was not done right.

I have a 2000 that I have only had for a 1/2 year now and it has always behaved like this. Since I was not an original owner I have no idea what these SUV's felt like new. I would really like to hear from someone who has had one of these since new. I have been unable to find any info on the encoder motor function/testing.

Mine made terrible clicking when turning with the wheels close to full whell lock. The transferr case fluid change made the terrible noise go away. I hear/read from many that this is a common condition and that they are often told this is normal. I suspect that these vehicles did not do this new nor is this normal.

Since I only use this to tow a boat in summer I have not spent any more time diagnosing but I would like to find a pdf of a service manual and get to the bottom of this.

redddogg60 · #8 01-28-2008, 02:07 AM

Before installing new encoder motor unit, my '98 Bravada would not go into all-wheel drive(I was getting stuck on snow/ice covered hills). I changed my automatic transfer case (ATC) fuse three times in one week, still no all-wheel drive. After reading other posts...I asumed the next logical thing to do was to change incoder motor. Now it seems to be stuck in all-wheel drive. I 'm close to giving up. Unless someone else can offer an easy fix. I just keep driving it this way. It's to old to dump $1000's into fixing it. If I get some extra time I will pull encoder motor myself and make sure it was installed correctly!

old_master · #9 01-29-2008, 06:13 PM

The NV 136 is a single speed automatic transfer case. The transfer case is in 2WD unless there is a difference in drive shaft rotation speed front to rear. If it detects a difference, the TCCM commands the encoder motor to engage 4WD. The encoder motor may be stuck in 4WD or inoperative. A difference in tire size, (circumference) front to rear can also cause 4WD to engage due to the drive shafts rotating at different speeds. Is the "Service AWD" light on?

matt_o_70 · #10 01-29-2008, 07:51 PM

Old_Master - what is your level of expertise? I worked for Toyota for several years before a career change. so I know my way around a wrench but I have zero GM experience.

Can I test the encoder motor and sensor easily? will the TCCM report codes and show encoder signals if connected to a OBDII scan tool (I am use to the enhanced features allowed by the factory tools)? "Service light" on my vehicle not light.

DO you have any experience with the alldatadiy.com service procedures - complete enough to include these tests?

Anyone have any OBDII software or a tool that they recommend.

old_master · #11 01-29-2008, 08:59 PM

Quote:

Originally Posted by matt_o_70

Old_Master - what is your level of expertise? I worked for Toyota for several years before a career change. so I know my way around a wrench but I have zero GM experience.

I've been around the block a few times. If I had to work on Toyotas, I'd change careers too. One of the nice things about GM, is their shop manuals are in English, not Japanese, and that alone makes them much easier to work on

Check your AF inbox.

redddogg60 · #12 01-30-2008, 04:34 PM

Tires are quite new, tire pressure is at spec levels, service AWD bulb is working but does not stay on(as to indicate problem). What should be my next move??? Thanks!!!

old_master · #13 01-30-2008, 07:18 PM

Your idea in post #8 of pulling the encoder and checking it for damage is a good idea. Check the connector and wiring for damage and/or corrosion also.

redddogg60 · #14 02-01-2008, 02:28 AM

Quote:

Originally Posted by Chris Stewart

It's been mentioned that it takes a few hundred miles to loosen the transfer case innards after the lube change.

Removing the front driveshaft will stop the binding but it also makes it 2WD.
You might make sure all your tires are the same size and you have 32psi in the front tires and 30psi in the rear tires. The most weight is over the front tires hence the higher air pressure to try to maintain the same tire diameter on all 4 tires.
I guess it's possible the encoder motor might've been installed in the wrong position...all help gratefully accepted.

After approx. 310 miles of driving my Bravada. The transfercase is finally starting to losen up. It still seems to bind very lightly when the steering wheel is cranked all the way. I can't thank you enough for your insight. I hope this post helps someone else. Thanks Again!!!!

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