Clunk with Control Trac???

[nitzoid]

I have a '97 EB, 4.0 SOHC,with Control Trac and 70k miles. Trans rebuilt 1500 miles ago. I recently experienced two problems. The first: Driving in 4AUTO, after overdrive kicks in (about 45mph), a "CLUNK" occurs with a slight hesitation when rpms drop to 1800, almost feeling as though it was attempting a shift. Occurance is random, but was happening a lot recently when on a snowy/icey highway. And on that occasion, the"CLUNK" was noticeable at varying speeds, with and without overdrive engaged. The second problem: engine dies while driving. Lights, radio, all electrics still function. After the first episode, had the fuel filter replaced. No problem for 7 months. Happened again that snowy night. Could this be a fuel regulator/relay thing? Any ideas?...Please.

 

[TPLYNCH]

Do you hear the clunk or feel it? Not sure if it would be the t/f case. Normally, if it is engaging, you will feel it through the steering wheel. You can try cleaning speed sensors. If they are dirty, might cause the 4x4 to engage. Otherwise, you may need your GEM reprogrammed if it is the T/F case and the speed sensors are OK.

Engine cutoff sounds like a problem with the Fuel pump relay or the pump itself. I'd start by checking the relay under the hood - cleaning the contacts to start then replacing if the problem persists.

 

[nitzoid]

I both hear and feel it (the clunk/hesitation), but not thru the steering wheel. More like beneath me. It feels/sounds like a bad U-joint of a rear-drive car in the old days. The fuel pump relay makes sense for engine cutoff.Thanks for the info, TPLYNCH.

 

[JDraper]

Another possibility for the clunk and rpm drop is the torque converter lockup. Did they replace your torque converter when they rebuilt the tranny? Have you tried running it in 4Hi to see if it occurs then? If it doesn't occur in 4 Hi, it's probably the xfer case and then a GEM reprogramming might be in order. I believe there was either a recall or a TSB on the GEM reprogramming to get rid of drivetrain noise. If it still occurs in 4 hi, I would suspect either a bad universal or maybe the torque converter is not locking up properly.

 

[dogfriend]

I ran across this article while looking for info on the Control Trac transfer case:

www.atra-gears.com/gears/2002-09/2002_09_60.pdf

Hopefully this isn't the problem, but it sounds like a possibility.


This unit is prone to certain
mechanical problems that are beyond
the scope of most shops to repair. The
most common mechanical failure is a
complaint of a loss of drive accompa-
nied by a ratcheting noise coming from
the transfer case during coast or decel-
eration or when in reverse. Careful
questioning of the driver will reveal that
this condition was preceded by an occa-
sional thump from the transfer case at a
constant road speed of 40-60 MPH.
When you disassemble the transfer case
you will find that the range hub and
range fork will be damaged, but replac-
ing these items will not solve the prob-
lem. The range hub is helical cut gear-
ing and will stay in mesh under load,
but will move out on coast due to the
thrust loads generated by the helical
design. Adding power will cause the
gear to return to the correct position.
The bottom of the teeth get chewed up
and the constant pressure on the fork
causes it to burn up. The real cause of
the problem is an offset in the centerline
distance, putting the shift rail at an
angle, which allows the range fork to
move out of position. The cases are
magnesium and we do considerable
machine work to correct this problem,
which is beyond the equipment found in
the average shop. If you see units with
this damage, you will usually see
oblong holes in the cases where the
shift rail rides. It is cheaper and more
efficient to buy a unit that has this
problem corrected than to tackle it
yourself.

 

[nitzoid]

When the tranny was rebuilt, an exchanged rebuilt tourque converter was installed. I haven't tried the 4Hi test yet. What kind of $ are we talking about:transfer case, GEM reprogramming, etc.? Thanks for the replies.

 

[Stephen]

My tranny was rebuilt at 70,000 miles and the Control Trac wasn't nearly as smooth until they did the reprogram, that helped. They didn't charge me at the Ford dealership that did the tranny rebuild, but I'm buddies with the service rep so I don't know if that was why.