2000 Jeep Grand Cherokee/ Transmission Slipping at high speed

[James]

I have a 2000 Jeep Grand Cherokee, 4.7 liter engine. Just today, the
transmission started "slipping" when increasing speeds above about 60 mph.
In other words, if I am travelling along at 60 mph and want to increase up
to 70 mph, I can feel a slight "shudder" when I accelerate. I don't know
if I am describing the sensation correctly but it feels to me like the
transmission is slipping. However, if I very gently increase the speed
from 60 to 70, it will not slip.

I have no problems accelerating from zero to sixty, even if I push it hard.
In other words, I can really dog it from a standstill up to 45-50 mph, and
it will shift through all the gears very smoothly and normally. So, it
appears to be slipping only in the highest gear, and then only when
accelerating at high speeds. By the way, my engine doesn't race up during
these "slips" or shuddering sensation....perhaps the slips are too brief to
cause the engine to rev up higher ???

Is there likely a "fix" to this, or need I worry about needing a new
transmission ? (I checked the transmission oil, and the level was fine,
and the fluid looked clean. I have had it serviced at normal intervals.)

Does this year 2000 transmission have adjustable bands, or is that only on
much older models? Could it be the transfer case causing this problem ?

Isn't it a good sign that the transmission shift smoothly and normally
through all of the gears, even when pushed pretty hard ?

Any ideas or comments would be appreciated !!

James

[DougW]

First thought is sag or missing. This can be caused by poor spark,
low fuel pressure (filter clogged). Highway speeds tend to bring
these problems out.

There are certain times where the transmission will behave badly.
Most recently I had some real fun with a highway downshift and hiccup.
Turned out it was a faulty Throttle Position Sensor. Go figure. :/
But my problem was at cruise (high speed) when fethering the gas.

Any engine codes?

There was a TSB for transmission slipping, but I think that was 2006.

--
DougW

[James]

Thanks for the reply Doug. Hmmmm , I had even thought about the
possibility of it being an engine missing or power problem. I will try to
get some codes, and will report if I get info. But, the "shudder effect"
surely made me think first of a slipping transmission, but it seems
important to me that it shifts real fine and smooth throughout the shifting
sequence.

Thanks again...

James

[DougW]

Shudder can be caused by the TCU getting bad information. This is
what I had and it liked to drive me nucking futs. There was this
one little spot where the transmission would hiccup and either stammer
or downshift.

After basically giving up on what else it could be, I bit the bullet
and installed a new TPS sensor on the ZJ. Night and Day.

Thing is, the TPS ohmed out properly and tested just fine. After
going a few days on the new one I tore the old one apart and sure
as shit there was a little worn/brown spot. Got so pissed off
I threw it over the house and probably into the neighbors back yard. :)

--
DougW

[James]

Thanks to Doug for pointing me in the right direction on this one. I
started out (see subject header) thinking I had a transmission problem, and
Doug reminded me that I could have some sort of engine misfire problem.
Well, as it turned out, I needed new spark plugs, and one coil !!! My
transmission is fine !!! (Good news !!)

The mechanic put in his notes that my old plugs had about 150K miles on
them, but he was wrong.... when I got home and looked up my car records, I
see these plugs had 185K miles on them !! So, my mechanic was wrong !!!
hee hee heeee

Runs great now !!

Thanks Doug, for keeping me out of the transmission shop, and getting me
pointed in the right direction for my mechanic to check out...

James

[DougW]

Not a problem.

Glad it was something less expensive than a trans.

I keep my plugs for about 10,000 miles. Good ol
AC Delco copper tip. :)

--
DougW

[James]

My mechanic said he never saw anything like it before... there was no tip,
the tops were flat across.... I wish he had saved them, but i was rushed
when I picked it up... they fired ok, except when accelerating at higher
speeds, then they were misfiring badly... so bad the car shuddered and I was
sure my transmission was giving out !!

thanks again Doug !!

(this newsgroup seems dead !!)

James

[DougW]

James wrote:

> (this newsgroup seems dead !!)

We had a problem a few years back with
crossposting trolls and general assholishness.
That basically killed off what was a thriving
news group and drove a lot of people to forums
where the trolls could be silenced.

A few of us remain, but it's no where near what
it was in 93 when I first joined.

--
DougW

[Will Honea]

DougW wrote:

> I keep my plugs for about 10,000 miles. Good ol
> AC Delco copper tip. :)

Doug, wht's the Champion number for those copper tipped plugs? I'm due and
I'm having a heck of a time finding them. My 88 MJ eats the fancy platinum
jobs. The Bosch plugs last a few hundred miles then goes titsup every time
while the Champions last a whole lot longer but I've always had a problem
finding them.

--
WHonea

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[Mike Y]

"James" <jnipp...@nospamfdn.com> wrote in message
news:ToidnX2hMo5AlxPT...@posted.localnet...

My 93 Intrepid would surge on the cruise control. Turned out to be plugs
and wires, with about 160K on them. Everything was fine when I drove it
normally. But on cruise it would surge and seem to slip. Since it drove
normally by the pedal, I never thought of the tranny as a possible cause, so
I didn't relate to your problem, but I think the cruise issue would seem
like you.

Anyway, changed the plugs and wires, and it was fine. Mileage went from
18-20 per tank to 25-26.

[DougW]

Will Honea wrote:
> DougW wrote:
>
>> I keep my plugs for about 10,000 miles. Good ol
>> AC Delco copper tip. :)
>
> Doug, wht's the Champion number for those copper tipped plugs? I'm
> due and I'm having a heck of a time finding them. My 88 MJ eats the
> fancy platinum jobs. The Bosch plugs last a few hundred miles then
> goes titsup every time while the Champions last a whole lot longer
> but I've always had a problem finding them.

Tried summitracing.com RC12LYC I think.

My standby is Autolite 3924, also a copper tip. It is a couple
of ranges cooler than stock. Have to run colder plugs because
of the blower.

--
DougW

[Lon]

The ignition system can fire some pretty heavily worn out plugs/wires.
I kept meaning to get a round tuit to replace my plugs, until about 140K
when the engine would just barely misfire at idle, and on climbing
canyons, the xmission would shift funny. Turned out my plugs probably
looked like yours, but the ignition was trying hard enough on the worst
one it cooked the wire a tad.

Odd, didn't really notice much difference in mileage, but the ZJ is
notable only in being better than my old RX-7 on mileage.