96 Control-Trac Transfer Case Binding

[CRS8205]

This is my first post. I have looked through many of the excellent threads here regarding the BW4405 TC but have not been able to solve my problem.

I have a '96 Explorer XLT 4.0l v-6 with the Control Trac BW4405 transfer case and a manual 5 spd transmission. I have had the explorer since it was new and it currently has 209k miles.

The 4wd switch has the 2WD, 4WD Auto, 4WD LOW options.

About October of last year I noticed that when I switched the 4wd switch to 4 WD Auto, the explorer would "bind up" on turns. This was while using it on dirt roads with packed snow. I have used the Explorer in similar conditions and this was not normal. I had been gone for a couple months this winter and have just now gotten back to look at this problem.

I have done some tests and it looks like the electric clutch on the TC is locking up completely like if you have done the "Brown Wire" mod. The front drive shaft is free in 2wd but locks up firmly when in 4wd.

Now that I have given you some ideal to the problem, I have a couple of items that could be causing the problem.

First, in August the Explorer had problems with the engine computer and my mechanic replaced the old computer with a remanufactered computer he bought from NAPA. I had not noticed the problem before that time so is there any possibility that the new computer could be bad or have the wrong programming? I cannot find any information whether the engine computer has any connection with the control-trac system.

Secondly, about 2 years ago at 190k miles I had the same mechanic replace the clutch. At that time, he also replaced the oil in both the manual transmission and the transfer case. I do not know what kind of oil he put in but I recall that he said he put some sort of "special" oil in. The receipt for the repair shows transmission oil and also a "molly additive". I don't know if he put the molly additive in both the transmission and the TC.

There are a number of threads discussing the issues regarding MERCON/ MERCON V so I am wondering if the oil could be causing the problems. Today I picked up some Vavoline DEX/MERC ATF and replaced the oil. I did not see any debris in the oil I drained but it was pretty dirty. When I transferred the oil into another container it looked "foamy" and seemed to want to seperate. I took it for a short test drive but the AWD is still binding. I might take more driving to fully see if this makes any difference.

Any ideals regarding this problem is appreciated.

 

[HahnsB2]

From reading around in the stickies your T-case should be doing this

The C-Trac transfer case transmits torque to the front wheels through an electromechanical shift assembly after a predetermined change in speed between the front and rear driveshafts is detected. These driveshaft speeds are determined by two Hall effect sensors which send a signal to the generic electronic module (GEM). If the GEM detects a change in speed between the front and rear driveshafts, it activates the transfer case clutch coil with a varying current to minimize the change in driveshaft speeds.

It seems as if the front output is staying locked instead of changing speed, causing the natural binding in turns that 4x4s get.

 

[mudbug0426]

i have the same problem with my 96, only i have an automatic transmission. when i have it in 4x4 if im not in mud, the transfer case will bind up really bad.

im not sure if it hurts anything, i would think it does. but its really annoying not being able to keep it in 4x4 without it binding

 

[gijoecam]

There are a couple things that come to mind... first and foremost, it's obvious that there's nothing mechanically wrong with teh case, as you tested to make sure it spins free in 2wd. The first thing that comes to mind is a front or rear output shaft speed sensor on the transfer case that's not reading correctly. The only way to know for sure would be to have an NGS or WDS scanner connected and watching the GEM PID's as the vehicle drives. One of the signals is likely out of range or dropping out when it shouldn't be, making the GEM think that the front and rear axles are turning at drastically different speeds and locking the t-case. You could take a shot at it and replace the speed sensors, but if the issue is in the wiring, changing the sensors won't make a lick of difference.

Now, if it was mine, I would simply leave it the way it is and use it like a conventional shift-on-the-fly transfer case. If it's binding in 4auto (we'll call it 4high for all intents and purposes) shift it back to 2wd. If you need the extra traction, shift to 4(high).... But that's just me. I realize that it doesn't actually fix the problem, I'm just sayin'....

Good luck!

 

[CRS8205]

There are a couple things that come to mind... first and foremost, it's obvious that there's nothing mechanically wrong with teh case, as you tested to make sure it spins free in 2wd. The first thing that comes to mind is a front or rear output shaft speed sensor on the transfer case that's not reading correctly. The only way to know for sure would be to have an NGS or WDS scanner connected and watching the GEM PID's as the vehicle drives. One of the signals is likely out of range or dropping out when it shouldn't be, making the GEM think that the front and rear axles are turning at drastically different speeds and locking the t-case. You could take a shot at it and replace the speed sensors, but if the issue is in the wiring, changing the sensors won't make a lick of difference.

Now, if it was mine, I would simply leave it the way it is and use it like a conventional shift-on-the-fly transfer case. If it's binding in 4auto (we'll call it 4high for all intents and purposes) shift it back to 2wd. If you need the extra traction, shift to 4(high).... But that's just me. I realize that it doesn't actually fix the problem, I'm just sayin'....

Good luck!

This is pretty much what I figured. Do you know where I can get more info regarding the NGS or WDS scanners? Will the normal OBDII scanners show the 4WD functions?

Leaving it as a full-time 4wd does not work good for my situation. Where I live we have rapidly changing road conditions where the 4wd Auto works very well. In a mile of driving, conditions go from dry to icy to packed snow to slushy and back to dry again. Due to these conditions I will just leave the TC in 4WD Auto and let it do its job which it has done very well.

The mechanic that changed the engine computer mentioned that he found a pinched wire that he fixed. I will need to check with him and see where that wire is and also what capability his scanner has.

 

[CRS8205]

Does anybody have a source and part number for the shaft speed sensor. Napa is the only parts store near by but I was not able to find it on their web site. I checked a couple of other sites but did not have any luck.

Thanks