Stuck in 4wd low.....

[Zack1978]

Hi everyone,
I needed to use 4wd today to pull out my trailer with my 99 SOHC, and when I went to put the truck back in 2wd(AWD) it would not move out of 4WD low. It does not matter what position you have the dash knob in, it is just stuck in low. I know the proper way to get it out of 4wd, but now something is broken. On the dash the O/D off light is lit, and both the 4wd high and low lights flash at the same time. At this point the truck is stuck in my driveway, since I can't drive it in low. Is there something easy that I can do to get it back into 2wd so at least I can drive it? Any idea as to the problem? IS this an expensive fix?

Thanks,
Zack

 

[drdoom]

Do some research on the shift motor (encoder). I believe you can remove it and make the shift manually with pliers. It is marked H-N-L.

 

[IZwack]

Been covered many times. Are you shifting it properly (neutral, foot on brake, etc...)? If so, try disconnecting the battery for a few mins first and see if the computer can force reset the shift motor.

 

[Zack1978]

Been covered many times. Are you shifting it properly (neutral, foot on brake, etc...)? If so, try disconnecting the battery for a few mins first and see uf the computer can force reset the shift motor.

Well as you noted, it has been covered. I disconnected the battery, and when I reconnected the battery it did go back into 2WD...like magic. Before I disconnected the battery, you didn't hear ANY sounds from the X-fer case motor or otherwise...as soon as it was reconnected I heard all the normal sounds and back to 2WD it went.

So......given the fact that the battery trick worked, where might I look to track down this problem? I read something about "wheel sensors"? Is that a probable cause? If so, where are these wheel sensors, and how difficult are they to change? What else may be an issue?


Thanks,
Zack

 

[IZwack]

Well as you noted, it has been covered. I disconnected the battery, and when I reconnected the battery it did go back into 2WD...like magic. Before I disconnected the battery, you didn't hear ANY sounds from the X-fer case motor or otherwise...as soon as it was reconnected I heard all the normal sounds and back to 2WD it went.

So......given the fact that the battery trick worked, where might I look to track down this problem? I read something about "wheel sensors"? Is that a probable cause? If so, where are these wheel sensors, and how difficult are they to change? What else may be an issue?

It is, as you said, "magic". It's been a while since I've dealt with this issue so I'm not sure if the wheel sensors are the culprit so I can't really verify whether they are what's causing the issue.

But having said that, I don't know what type of a trailer (car, horse, etc..) you have and how heavy it is but if I were you, I would avoid going into LO range unless you absolutely positively need it. The LO range system (and for that matter, the entire electronically shifted 4wd system), as you found out, isnt exactly as reliable as it should be. It works most of the time, but every now and then, you'll find yourself up the WTF-why-wont-this-work creek without a paddle. So I would try to avoid shifting into 4LO and just stick to AUTO or 4HI (as shifting between AUTO and 4HI is not a gear change like 4LO, but rather just an engagement of a friction plate stack - based clutch system).

 

[Zack1978]

It is, as you said, "magic". It's been a while since I've dealt with this issue so I'm not sure if the wheel sensors are the culprit so I can't really verify whether they are what's causing the issue.

But having said that, I don't know what type of a trailer (car, horse, etc..) you have and how heavy it is but if I were you, I would avoid going into LO range unless you absolutely positively need it. The LO range system (and for that matter, the entire electronically shifted 4wd system), as you found out, isnt exactly as reliable as it should be. It works most of the time, but every now and then, you'll find yourself up the WTF-why-wont-this-work creek without a paddle. So I would try to avoid shifting into 4LO and just stick to AUTO or 4HI (as shifting between AUTO and 4HI is not a gear change like 4LO, but rather just an engagement of a friction plate stack - based clutch system).

OK, so if I leave the dash switch alone in the "auto" position, I "should" still have 4wd....just not 4wd low? This situation will drive me nuts, so I would like to fix it once and for all. The speed sensors seem to be somewhat cheap on Rockauto.


Zack

 

[IZwack]

OK, so if I leave the dash switch alone in the "auto" position, I "should" still have 4wd....just not 4wd low?

Yes because: AUTO allows the computer to decide when to engage 4HI (which is 4wd - HI range) based on the data it is reading from the driveshafts' RPMs. So yes, if you put the switch to AUTO, then yes the vehicle will engage 4HI when it thinks it needs it. However, if you put the switch into 4HI, you are basically demanding the vehicle to engage and stay in 4HI.

We should note that engaging 4HI does not involve the shift motor at all, it is an engagement of a stack of clutch/friction discs via a large electromagnetic ring inside the transfer case. 4LO (which is 4wd - LO range) is the odd one because, as mentioned before, in addition to engaging the stack of discs, it also changes a gear set (a planetary gear set to be precise) inside the transfer case and this changing of a gear set requires the shift motor.

 

[drdoom]

Take them out and clean them, then do a test on them with a meter.

 

[Zack1978]

Take them out and clean them, then do a test on them with a meter.

Ok, I will do that. Is there a "how to" thread? Where are these sensors located? Are they easy to R&R? Besides these sensors is there anything else that could cause the problems that I have?

Thanks,
Zack

 

[DanaM]

I still love this forum Stuck in 4wd low and now I know what to do.

Thx!


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