4wd hi/lo lights flashing

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BillM - 06 Oct 2005 03:35 GMT

I've read a little about this problem before.
1998 Explorer XLT 4WD
Both the 4WD HI and 4WD LO lights flash 5 times every few minutes.
From what I'd read, the problem is usually either a poor connection to the
speed sensor or the speed sensor itself.
Apparantly there is a TSB out on it.
I called the dealer and they said it's a common problem, and estimated it
would be $225 to fix.

So here's where I might have gone wrong. I took it to a local shop a few
blocks from my house (the dealer is a little ways away).
They spent two days diagnosing it and said it's a shift motor and wire
button, and the parts alone are $391, plus labor for diagnosis and install.

So here's my question - does this sound right? I know you can't diagnose a
car over the internet, or over the phone, but there seems to be a big
difference here. I told them to hold off doing the work until I can do some
research.

Thoughts, anyone?

BillM

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Vic Klein - 06 Oct 2005 14:04 GMT

Doesn't sound right at all. The '98 Control Trac system only uses a shift
motor to get into low range, otherwise it isn't seen at all. It would not
report a problem in normal driving, only when failing to shift in or out of
low range. You are correct that the likely problem is simply a speed signal
issue caused by crud on the speed sensors (especially after a number of
years). A replacement sensor is relatively inexpensive and you might only
need to pull them and clean them off. These are Hall-Effect sensors that
read the passage of teeth on a gear to generate pulses for the GEM compouter
to compare front and rear axle speeds. In any gearbox there is a gradual
accumulation of fine metal bits from the normal wear and tear that takes
place. Some of the lubricant gunk containing fine metal bits that builds up
on the sensor end and on the "tone gear" can gradually mask the signal
making it erratic or non-existant. I'd try cleaning them first. There are 3,
as I recall, and all are mounted to the transfer case.

=Vic=
Bear Gap, PA

> I've read a little about this problem before.
> 1998 Explorer XLT 4WD
[quoted text clipped - 18 lines]
>
> BillM

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News - 06 Oct 2005 22:56 GMT

Hi
I had exactly the same problem a few weeks ago.
I got underneath, waggled the wires around the sensors and disconnected the
battery for half an hour.
Hey Presto, no more problem.
I but it goes again now I've posted this :-(

Signature

Best Wishes

Len Smith
Ravenstone Model Railways
Leicestershire UK
lensmith@rmrailways.co.uk
http://www.rmrailways.co.uk

> I've read a little about this problem before.
> 1998 Explorer XLT 4WD
[quoted text clipped - 19 lines]
>
> BillM

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