4WD Engaging Automatically . . .
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4WD Engaging Automatically . . .
Has anyone had experience with or heard of a case where a 2004 Screw went into 4WD by itself?
Three times during the last week, while decelerating or coasting, a grinding noise - sounded like metal on metal - could be heard above radio noise, etc. Upon slowing down to stop and check it out - a loud clunk occurred and the noise disappeared. Afterwards - everything sounded and felt normal. The last time, the entire truck shuddered and the engine seemed to rev up - I was going about 20 mph approaching a stop light. When nearly stopped, another loud clunk/thump (entire truck lurched a little) occurred. The rest of the trip home (14 miles) and the next day's trip to Ford was uneventful.
Fortunately - while the service techs were extensively testing / driving it - it happened to them also. How often does that really happen??? Anyway - they seem to think the 4WD is engaging on its own . . . . They didn't say 4H or 4L - but I would say 4L based upon what I felt.
They want the regional service person (can't remember the exact title) to look at it Monday.
Any thoughts.
'04 Screw - 8000 miles
Three times during the last week, while decelerating or coasting, a grinding noise - sounded like metal on metal - could be heard above radio noise, etc. Upon slowing down to stop and check it out - a loud clunk occurred and the noise disappeared. Afterwards - everything sounded and felt normal. The last time, the entire truck shuddered and the engine seemed to rev up - I was going about 20 mph approaching a stop light. When nearly stopped, another loud clunk/thump (entire truck lurched a little) occurred. The rest of the trip home (14 miles) and the next day's trip to Ford was uneventful.
Fortunately - while the service techs were extensively testing / driving it - it happened to them also. How often does that really happen??? Anyway - they seem to think the 4WD is engaging on its own . . . . They didn't say 4H or 4L - but I would say 4L based upon what I felt.
They want the regional service person (can't remember the exact title) to look at it Monday.
Any thoughts.
'04 Screw - 8000 miles
Cargo Master
Joined: Jan 2005
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i thought there was no way 4l could be engaged unless the tranny was in neutral.lord knows i,v tried a million times over the last 9 yrs to do it(forgetting to shift to neutral)but only getting 4h but then there is still murhy,s law.
Tuned
Joined: Dec 1999
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From: Bismarck USA
If I remember correctly, the front axle is engaged via a vacuum line. On the previous 97 style truck, loss of vacuum meant no 4 wheel drive. Someone had mentioned on here that they switched it so if you lost vacuum, 4 wheel kicks in.
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Joined: Jan 2004
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From: Marple Township, PA
jrroth...do you have electronic shift-on-the-fly?? Could be a wire is grounding out somewhere. The ESOF logic goes through the PCM also.
It would be pretty much impossible for 4L to engage randomly...but 4H could happen if something is shorting out.
Of course, if you have mechanical 4wd shift, that theory is shot!
But with all the wierd revving you describe, I'd lean towards a bad PCM.
Good luck!!
It would be pretty much impossible for 4L to engage randomly...but 4H could happen if something is shorting out.
Of course, if you have mechanical 4wd shift, that theory is shot!
But with all the wierd revving you describe, I'd lean towards a bad PCM.
Good luck!!
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It does have electronic shift-on-the-fly. I would agree that the 1st couple of times - it was definitely not going into 4L as I was travelling >50mph. Last time felt very different though. I wouldn't expect to hear any noise or feel anything if it was going into 4H at high speeds - at least I don't think so. Also the first few times it sounded as if the noise was coming from the rear wheels . . . .if that helps anyone.
I guess we'll see what happens Monday. They did tell me that the sympoms they experienced while test driving it have not been seen before (at least here locally).
I'll post when I hear more
JRR
I guess we'll see what happens Monday. They did tell me that the sympoms they experienced while test driving it have not been seen before (at least here locally).
I'll post when I hear more
JRR
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Originally Posted by 92merc
If I remember correctly, the front axle is engaged via a vacuum line. On the previous 97 style truck, loss of vacuum meant no 4 wheel drive. Someone had mentioned on here that they switched it so if you lost vacuum, 4 wheel kicks in.
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why would i want 4w to kick in at a loss of vacuum? just wondering.not sure somthing i need.
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Cargo Master
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Originally Posted by Justis01
If you were out 4 wheeling in soft sand and one of those vacuum lines failed, you wouldn't want that hub to disengage would you?
nope i sure wouldnt.... so reversing the vacuum to no vacuum solves that problem? i thought the vacuum engaged the 4w not mantain 4w.
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Well - The answer is:
Vacuum leak on LF wheel hub solenoid. And yes . . . 4wd does engage on loss of vacuum. Even the Service Manager isn't quite sure why it is designed that way.
Also had the PCM reprogrammed. BIG difference in responsiveness.
There does seem to be a little vibration in the steering wheel now however - not sure whether it is tire or engine rpm related.
JRR
Vacuum leak on LF wheel hub solenoid. And yes . . . 4wd does engage on loss of vacuum. Even the Service Manager isn't quite sure why it is designed that way.
Also had the PCM reprogrammed. BIG difference in responsiveness.
There does seem to be a little vibration in the steering wheel now however - not sure whether it is tire or engine rpm related.
JRR
