Im noticing a problem with my automatic 2007 GT while going uphill at low RPM in fifth gear. When my RPMs start to drop while going up a steep hill, it will get to about 1000 before it finally downshifts, but before it does, it feels like my power is cutting out and it stutters before finally shifting itself back down into 4th. I recently purchased this car with 124,000 miles and I don't think the tranny fluid, or the diff oil has ever been changed. is this problem common in the S197s?

 

You could start by changing the tranny fluid & filter, and change the rear diff oil (don't forget to add friction modifier).

 

will do sir

 

A agree with the guy above

 

If the transmission fluid has never been changed, you may make the issue worse. It is a 50/50 shot, so hope for the best and expect the worse.

 

First of all, the computer controls the shifting and at what RPMs, and looks at the
throttle position to determine load factor.

When the ECU commands the TCM to shift, it shifts. IF the ECU does not see the shift,
you'll get a MIL for the error. If bad fluid is causing the delay, when the trans is commanded
to shift, you'll get an error, the CEL light would come one or blink. It's simply not seeing a
load condition to downshift, or release the lockup clutch, which is all that it needs to do, first.

What is happening; the throttle position under load isn't justifying the downshift; the ECU
is not seeing the need to command a shift. The RPMs may be 1000, but the TPS data is
not showing the position for a load, for the downshift. It doesn't think it is on a hill, because
the TPS isn't advanced enough to either release the lockup clutch, or downshift. I have noticed
the older the car gets, the sooner the TCC locks up, and later it releases...

There used to be a separate TPS on throttle bodies, where you could loosen the bolts,
and advance the TPS slightly to correct the shift under load. You could oval out the
mount holes to advance or retard the TPS to correct shift issues.


For example, the TPS is located on the LEFT side of this TB unit.

You would loosen the two bolts, twist it backwards, hold it, and tighten the bolts, test drive.
If you get no movement from the TPS, you can oval out the holes to do it. Or, replace it
and test drive.

IF there is ANY mechanical failure that interferes with a shift, you will know about it. I do not
think it's a fluid issue, the shifts would be sloppy, harsh, or slip. Your trans is holding in gear,
TCC locked up, at low RPMs because the ECU does not SEE the need to act, it thkinks
your not on a steep enough incline because the TPS is not in a position to show it.

For example:
I have a boost module on my '15 TSI. It does the same thing, the lockup clutch does
not release when it's supposed to to because the TPS does not show the pedal position
needed for it, but I am still getting more boost an acceleration because of the module modifies
the sensor readings. I have to push down on the pedal farther than I did without it, and under
+6 lbs of boost, at 1000 RPMS in 6th, TCC locked up, I get a shuddering and growling
from the trans because the TCC hasn't released because the TPS doesn't show the ECU need
to release the TCC, but boost is still increasing. So, I have to press down more than usual.

 

yeah thats exactly whats going on with mine, the tranny will make a weird noise and start limping up the hill, and doesn't downshift until i press on the throttle some more. do you have a video on the process you suggested that I do?

 

DO not have a video, but you will want to tweak the TPS in the opposite direction the
throttle plate opens. You may also be able to take apart the fuel pedal assembly and
clean the contacts for the drive by wire. I saw a tutorial on that somewhere, and was
for Mustang. Might be in the How-Tos section, not sure...

I had a 2000 Dodge Avenger ES, and one of the tricks was to oval out the TPS mount
holes, then slightly turn it the opposite direction the TB Plate opens. This would help
with TCC lockup disengaging sooner. You should only need like 1mm of turn. A TPS
is basically a variable resister, and we all should know what happens to them when they
age.

 

Ill definitely try it out soon, thank you.