Yet another Auto 4x4 issue

[mikehenya]

Just bought an 02 and replace all 4 tires with brand new ones (yes balanced), all 4 wheel bearings, 4WD control module, all brakes, rear transfer case speed sensor and upper rear ball joints. The 4WD auto keeps kicking in and out, it seems to be much worse in the 1800 to 2000 rpm range.
I am trying to get it going to give to my daughter once winter was over, so I would PREFER not to do the brown wire mod. I would like it to work right for her. I am guessing that the motor is working because when you you put it in 4wd high it works fine. seems to have a little binding in the front, but I didn't play with it much. I pulled it back in when it "chattered" again.

I tried everything I have read so far, fixing the above things seemed to have cured hundreds of others postings, but not this one!! Anyone got any other ideas?? I'm not sure what else controls the system. Thanks!

 

[not8taxi]

i dont get what you mean by trying to fix the auto 4x4...your truck is always in 4x4 auto...its going to kick in or engage the front wheels when the car senses that it is slipping and give power to that wheel...the brown wire mod is just a way for people to mod their explorers from a 4x4 auto to 2wd...if your ex is 4wd and has the 4wd buttons on the dash it does not go into 2wd ever...it stays in whats called 4x4 auto...hope that helps...if anyone else has any more info they could post it...heres a link to another thread that was posted last week about the same thing.....http://www.explorerforum.com/forums/showthread.php?t=301505

 

[mikehenya]

Sorry, I didn't want to thread jack anyone else. I guess what I meant by "fix 4wd auto" is now I have to pull the number 17 and 18 fuses just to daily drive it now that I have fixed all those things. On a straight dry road it keeps acting like the tranny is slipping (but it's not) in and out of 4wd until I either put it into high or pull the fuses.

 

[2TimingTom]

VSS- vehicle speed sensor?

 

[mikehenya]

I changed the one in the rear diff, plus the 2 that control the ABS in the front bearings are new (included with the bearings). Is there another hiding somewhere? I expected one in the tranny, but can't find a reference to it for 02.

 

[2TimingTom]

In the 2nd gen X's, it's in the transfer case.

 

[mikehenya]

I just did the BWM and it seems to work fine. I would like to get it working the correct way for her for winter if I could and use the BWM in the summer. Any other thoughts?

 

[joecrna]

So you mean the 4WD auto is engaging the front drive shaft even when it shouldn't be. The system thinks it sees a difference in the front and rear wheel speed. First the obvious, are all tires exactly the same diameter? Now how do these systems determine wheels speed? Lots of ways. ABS sensors, VSS and the possible cause of your problems assuming the GEM and 4x4 module are functioning correctly. There are 2 Hall effect sensors inside the transfer case. They compare front and rear driveshaft rotational speeds and provide data to the control module. It than backfeeds current, via the brown wire, to the electromagnetic clutch in the T-case. When in 4WD high you by-pass this and send current down the brown wire without additional input from the control module. Remember, there are other ways the GEM and 4WD control module sense vehicle speed but my bet is your problem is one of the Hall effect sensors.

 

[mikehenya]

That is exactly what I mean.Well, I replaced everything you listed except the 2 "hall effect" sensors and the GEM module itself(see first post). Even the 4wd Modulke and sensors are brand new. Are the Hall sensors something you can get at without tearing it down? I don't see them in the Haynes, but I'm still looking as we speak....
What is more likely the GEM module or the Hall effect sensors???

 

[mikehenya]

Well, Haynes is worthless on this one! "Due to the complexity of the transfer case...blah blah blah take it to a mechanic" ! Why do they think we buy the darn book!

 

[joecrna]

Unlikely the GEM, it smiply processes and transfers some of the data. Look at the sticky in the transmission and transfer case forum under "transfer case rebuild diary". Glacier did an excellent job as usual. The Hall effect sensors are deep in the T-case but he shows you pictures. They are actually little more than tone rings just like ABS sensors. Diagnosing (pulling codes) in the T-case and trans require expensive specialized code readers. I finally gave up after failing to gain full access to a Ford "trans reader" (not the real name). Not even all Ford dealers have one. My local Gallpin Ford did. Be prepared for a sizable bill for the fix. In Ohio, Richart Ford should have one but ask around. These are actually called NGS or WDS scanners, had to look that up again.

 

[mikehenya]

Wow...Nice read! Thanks for the point in the right direction Joe! Glacier did some great write ups!!! I wish I knew if that was the problem!