Help me diagnose this...

[TequilaSnrs087]

Help me diagnose this... *edit* lights flashed again

My Explorer is a 95 with the BW 4405 t-case and Control Trac. A while back, I shifted it into 2WD from 4WD Auto. The 4WD Auto light in the gauge cluster turned off and I started down a paved road. About a mile down the road, both the 4WD Auto and 4WD Low lights began flashing. I pulled over, shifted the truck into neutral, turned it off and restarted it. Everything was fine after that. I know it was in 2WD because the axle disconnect wasn't making its normal racket that it would in 4WD. A short time later I took it to a local shop to have the transfer case fluid changed (apartments won't let me do it at home). For whatever reason, they put it in 4WD, and it got stuck in it. They said it would not come out of 4WD, but that they would get it back into 2WD for me. Looking at the shift motor, it appears to have never been removed, so I can only assume they tapped on it or something to get it to shift. So anyway, does this definitely sound like the shift motor? I don't really want to go around replacing parts until I have a good idea. When I start the truck, both the 4WD Auto and 4WD Low lights illuminate and go out like they should, so I assume this is not a problem with the GEM module or the lights would flash, correct?

 

[TequilaSnrs087]

I guess everyone can disregard this post, everything seems to be working fine now. I had not tried to use 4WD since it had become stuck in it at the shop. I didn't want to have the shift motor go completely at an inconvenient time. Curiosity got the better of me today though and I tried it out. The t-case shifted flawlessly in and out of all ranges. I used 4WD on a dirt road with no problems. I know it was engaged too because I heard the shift motor and I heard the usual noise from the front axle disconnect. I guess either the shop didn't know how to use the 4WD switch, it was binding up on something, or maybe the 'Sploder just likes me. Who knows. Anyway, I'm just happy my 4WD is working.

 

[Mbrooks420]

The lights flashing is like a Check Engine Light for your 4wd system. The transfer case not shifting just means the motor is probably dirty. It's an easy job to pull and clean.

 

[TequilaSnrs087]

The lights only flashed that one time. It has not done it since. They do come on at start up with all the other lights that should and turn off like they should. Everything is working fine now, so I guess it is nothing.

I do plan to do some waterproofing and cleaning under the truck when I have the time.

 

[gijoecam]

If it only does it one time, don't sweat it. If it does it again, there's gremlins we need to run out of it.

Also, for the record, the 2wd to 4-high shift does not involve the transfer case shift motor. The motor is only involved with the high/low range selection. Lockup is handled by the transfer case clutch coil, controlled by the GEM and TOD relay. Barring mechanical failure, or a sticking switch, it's impossible for it to get 'stuck' in 4high. I suspect they weren't following the correct procedure at the shop and managed to get it stuck in 4low because they were trying to shift without their foot on the brakes or with the vehicle in park.

 

[TequilaSnrs087]

I guess I was hearing a relay or something when I put it into 4 auto. It was just a faint noise, vs. the loud clunk for 4 low.

 

[TequilaSnrs087]

I'm bringing this back up because everything may not be well.

Before I start with today's issue...is it okay to use the auto mode on pavement? Today it was raining and I figured I would throw it in auto since everything I have read, including the owner's manual, seems to say that it is okay to use on paved roads if needed. The owner's manual says that it may be engaged at any speed and makes no mention about not using it on pavement. It does say that 4 low must be used only off pavement. I am mostly familiar with 4 high/4 low systems that are entirely for off pavement use and the auto 4WD thing and its limits are new to me. So is the auto mode not for use on pavement either? Is my auto mode different from later Explorers that only have auto/high/low?

Anyway, what happened today was that I threw it into 4 auto during some heavy rain. All was well until I hit about 40 MPH. I got the flashing lights, followed by both 4WD lights going off with the switch still in 4 auto. Tried it again, same deal. Everything was fine until about 40 MPH when I got flashing lights. Below 40 MPH, it stays in 4WD with no issues as long as I like. I took it down some dirt roads doing 25-30 MPH and it was perfect. Why is it that it is going nuts once I hit a certain speed? There are no unusual noises, vibrations, anything.

I am wondering if maybe the CV axles could be to blame? Both were replaced recently due to damaged boots. Is it possible that the shop installed them improperly or something? Everything else with the 4WD system is original. Both axles are filled with 80W90 Motorcraft fluid, all tires are the same size and type, 31s, filled to the same pressure.

Also, does the auto mode rely on wheel speed sensors at all? I wonder if the 31s are throwing it off? They can't be off by much, I tested the speedo against a handheld GPS unit and it was very close, but the tire size would explain the issues occuring only after 40 MPH since the speed will be off more at higher speeds.

 

[Mbrooks420]

Auto can be used on pavement, as the 97 and ups are always in auto, there is no 2wd setting. You'll need to have the codes read for the flashing lights. Taking wild guesses won't likely help you fix it. I highly doubt the cv shafts could effect anything, and the 31's should be fine since they are all the same. Lots of people run oversize tires with the BW4405 transfer case.

 

[gijoecam]

Ditto. 4auto is fine anytime and anyplace. The problem is likely a speed sensor dropping the signal above 40 mph, but without knowing the code that's stored, it's impossible to diagnose. You can take a shot in the dark and replace the rear axle speed sensor on the rear axle for about $13, and that *might* fix it, but again, without knowing the code, it's a guess at best. The rear axle speed sensor is the culprit about 1/4 to 1/3 of the time.

-Joe

 

[TequilaSnrs087]

Alright, thanks for the responses. Can only dealerships read GEM codes? How much does that generally run?