Jeep Gr. Cherokee trans problem

I have a 1997 Jeep Grand Cherokee Limited w/ 55,000 miles, up country
suspension.

This vehicle is NOT driven daily, perhaps once every two weeks.

I had the transmission flushed and refilled at about 52,000

Last night while cruising on the highway at about 60 mph, the transmission
"shifted" once very hard, so much that my passenger noted and asked what was
wrong with the vehicle.

This has happened maybe 3 times previously within the past two months, at
highwasy speed and at low speed around the city.

Any ideas of what could be going on?

You are not alone. I have a 97 GC Orvis with V*, Up Country, trailer
tow. I get the same surprise shift about every three of four days.
Its a daily driver, long on weekends and short trips during the week.
Been happening for about a year, nothing ill (yet). Both at highway
speed and also the 1-2 shift.

It almost seems like the trans can't make up its mind whether to go
into overdrive or not.

Its due in for service in late October and I'll have it checked then.

> I have a 1997 Jeep Grand Cherokee Limited w/ 55,000 miles, up country
> suspension.
>
> Last night while cruising on the highway at about 60 mph, the transmission
> "shifted" once very hard, so much that my passenger noted and asked what was
> wrong with the vehicle.
>
> This has happened maybe 3 times previously within the past two months, at
> highwasy speed and at low speed around the city.
>
> Any ideas of what could be going on?

You folks need to replace your VSS (Vehicle Speed Sensor) before
your transmission eats itself. The VSS is what tells the computer how
fast the vehicle is going... when it lies, all hell can break loose. Should
have popped a code... have them checked.
__
Steve
..

"Howard" <[email protected]> wrote in message
news:[email protected]...
> You are not alone. I have a 97 GC Orvis with V*, Up Country, trailer
> tow. I get the same surprise shift about every three of four days.
> Its a daily driver, long on weekends and short trips during the week.
> Been happening for about a year, nothing ill (yet). Both at highway
> speed and also the 1-2 shift.
>
> It almost seems like the trans can't make up its mind whether to go
> into overdrive or not.
>
> Its due in for service in late October and I'll have it checked then.
>
> > I have a 1997 Jeep Grand Cherokee Limited w/ 55,000 miles, up country
> > suspension.
> >
> > Last night while cruising on the highway at about 60 mph, the
transmission
> > "shifted" once very hard, so much that my passenger noted and asked what
was
> > wrong with the vehicle.
> >
> > This has happened maybe 3 times previously within the past two months,
at
> > highwasy speed and at low speed around the city.
> >
> > Any ideas of what could be going on?

"" <[email protected]> wrote in message
news:[email protected]...
> Steve -
>
> Thanks for the tip.
>
> 1) Is the vehicle speed sensor an item that is easily
> accessible/replaceable for the home mechanic?

My experience is that it is easier on a Jeep than most other
vehicles... the sensor is on the transfer case on my XJ,
you can replace it with common hand tools just by crawling
under. Try replacing it on a Taurus... POS has to have the
Y-pipe dropped, among other things.

> 2) Is there a test that one can perform on this part to verify failure (I
> am an electronics type geek-access at work to lots of test equipment)

With an intermittent failure such as this, it's often more expedient to
just start replacing stuff, the easy/cheap stuff first. You may find it
full of fluid, a sure sign of failure.

> 3) I assume the VSS is an interface between the trans and computer
module,
> tells the trans when its time to shift. Am I close?

Exactly... you would notice things like cruise control dropping out,
or electronic speedo falling to zero. It should pop a code for wrong
speed in gear.

> 4) Any idea of approx cost to replace by the dealership?

Probably around $150... not sure. Like I said, it's very easy
to replace on an XJ, I'm not sure where it's located on yours.

> BTW - I did have my trans fluid changed by a quick oil change place. But
> that was performed about a year and a half ago. This problem has recently
> surfaced within the past 3 months. That and a noisy sound from the rear
> that sounds like a worn caliper constantly dragging on a rotor. The posts
> about GCL and problem rear diffs are scaring me.

I don't think they're related... VSS failure is a common thing, my sister
just
had one go out on her Honda ('92 Civic DX) last month. Luckily, she was
near the bosom of the family; I was able to call and have the part shipped,
then talk my brother through putting it in. Part was $120, but that's
Honda.

Get yourself some kind of manual... Haynes is cheap, and not so bad,
factory manual is better.
__
Steve
..

I haven't had that problem, but also have a '97 ZJ and had a related
problem you might check for. The transmission has an output shaft speed
sensor located on the lower left side of the trans right before the xfer
case. The VSS/speedometer sensor is on the rear portion of the transfer
case up toward the top. On mine trans fluid was seaping out around the
trans sensor into the electrical connection causing a trouble code. The
dealer changed mine under warranty, but it would be a simple DIY task.
The sensor is a nylon/plastic hex plug with a 2 wire connector. It might
be as easy as a dirty connector. I don't know which of the 2 sensors is
used for what or if one backs up the other in case of failure.

In article <[email protected]>,
[email protected] says...
>
> "" <[email protected]> wrote in message
> news:[email protected]...
> > Steve -
> >
> > Thanks for the tip.
> >
> > 1) Is the vehicle speed sensor an item that is easily
> > accessible/replaceable for the home mechanic?
>
> My experience is that it is easier on a Jeep than most other
> vehicles... the sensor is on the transfer case on my XJ,
> you can replace it with common hand tools just by crawling
> under. Try replacing it on a Taurus... POS has to have the
> Y-pipe dropped, among other things.
>
> > 2) Is there a test that one can perform on this part to verify failure (I
> > am an electronics type geek-access at work to lots of test equipment)
>
> With an intermittent failure such as this, it's often more expedient to
> just start replacing stuff, the easy/cheap stuff first. You may find it
> full of fluid, a sure sign of failure.
>
> > 3) I assume the VSS is an interface between the trans and computer
> module,
> > tells the trans when its time to shift. Am I close?
>
> Exactly... you would notice things like cruise control dropping out,
> or electronic speedo falling to zero. It should pop a code for wrong
> speed in gear.
>
> > 4) Any idea of approx cost to replace by the dealership?
>
> Probably around $150... not sure. Like I said, it's very easy
> to replace on an XJ, I'm not sure where it's located on yours.
>
> > BTW - I did have my trans fluid changed by a quick oil change place. But
> > that was performed about a year and a half ago. This problem has recently
> > surfaced within the past 3 months. That and a noisy sound from the rear
> > that sounds like a worn caliper constantly dragging on a rotor. The posts
> > about GCL and problem rear diffs are scaring me.
>
> I don't think they're related... VSS failure is a common thing, my sister
> just
> had one go out on her Honda ('92 Civic DX) last month. Luckily, she was
> near the bosom of the family; I was able to call and have the part shipped,
> then talk my brother through putting it in. Part was $120, but that's
> Honda.
>
> Get yourself some kind of manual... Haynes is cheap, and not so bad,
> factory manual is better.
> __
> Steve
> .
>
>
>
>

Steve Cowell wrote:
> "" <[email protected]> wrote in message
> news:[email protected]...
>> Steve -
>>
>> Thanks for the tip.
>>
>> 1) Is the vehicle speed sensor an item that is easily
>> accessible/replaceable for the home mechanic?
>
> My experience is that it is easier on a Jeep than most other
> vehicles... the sensor is on the transfer case on my XJ,
> you can replace it with common hand tools just by crawling
> under. Try replacing it on a Taurus... POS has to have the
> Y-pipe dropped, among other things.

http://members.cox.net/wilsond/Fixes/sensor-speed.jpg

The speed sensor is just a simple switch. Take it out and put
an ommeter across the leads. Spin the sensor and you can
see the circuit make and break.

>> 2) Is there a test that one can perform on this part to verify failure (I
>> am an electronics type geek-access at work to lots of test equipment)
>
> With an intermittent failure such as this, it's often more expedient to
> just start replacing stuff, the easy/cheap stuff first. You may find it
> full of fluid, a sure sign of failure.

The first thing to do is always check your connections. Remember what
happens to circuits when a ground floats?



--
-- DougW -- 93 ZJ 4.0 http://members.cox.net/wilsond
HESCO Supercharger - 300W IASCA Stereo - Edelbrock IAS Shocks
Gibson Exhaust - rear DCpower - custom gauge install - Stillen Rotors

Torque converter shudder can be pretty bad in this model also. But this
usually occurs around 47 mph if accelerating at a normal or slow pace. Mine
has been bad enough to shake the vehicle. You can test this by tapping your
brake pedal with your left foot while maintaining a steady speed above 50 or
so. If you watch your tach, you will notice the idle speed increase
slightly as the torque converter unlocks. Seconds later, the converter will
lock down again. Notice how it feels.
I had my trans serviced about 4000 miles ago (I have 110,000 on jeep) This
is the second time I have used a product called 'Dr Tranny Fix' (comes in a
small red tube, perhaps 2 ounces) with very good results. I have to really
pay attention to feel the torque converter lockdown now. I have used this
product since 70000 miles, and I am very pleased. Also, are you certain
that genuine chrysler transmission fluid was used when your vehicle was
serviced? Make sure that dexron was not used.

"" <[email protected]> wrote in message
news:4Q%[email protected]...
> I have a 1997 Jeep Grand Cherokee Limited w/ 55,000 miles, up country
> suspension.
>
> This vehicle is NOT driven daily, perhaps once every two weeks.
>
> I had the transmission flushed and refilled at about 52,000
>
> Last night while cruising on the highway at about 60 mph, the transmission
> "shifted" once very hard, so much that my passenger noted and asked what
was
> wrong with the vehicle.
>
> This has happened maybe 3 times previously within the past two months, at
> highwasy speed and at low speed around the city.
>
> Any ideas of what could be going on?
>
>