Transmission Won't Kickdown When Floored

[RobC100]

Im a brand new member. I have a 2004 Grand Cherokee Overland with a 4.7L V8 and a 545RFE transmission. It has about 98,000 miles on it. The transmission works fine around town with up and downshifting. On the freeway, with normal acceleration and deceleration, it also performs fine with no hard shifts. Transmission fluid is full and clear. My problem is that recently when I am getting on the freeway and need to floor it to move into traffic, the transmission refuses to downshift (kickdown). At that moment it has no power and acts like it is just refusing to accelerate any faster. I checked with my code reader and found zero codes.

Any suggestions or ideas? Thanks.

 

[JPNinPA]

Welcome!
And sorry i just saw this today.

What size tires?


Never look down on anyone unless you are helping them up - Jesse Jackson

 

[JPNinPA]

1801304 - FLASH: TRANSMISSION SHIFT/SPEED CONTROL IMPROVEMENTS
Date: 03/30/04 (supersedes 1800503c dated 08/01/03)

Model Year(s): 2003

Description: This bulletin involves selectively erasing and reprogramming the Powertrain Control Module (PCM) or the Transmission Control Module (TCM) with new software. NOTE: THIS BULLETIN APPLIES TO WJ VEHICLES EQUIPPED WITH A 4.7L ENGINE.

Details: Vehicle operator may experience:

1. MIL illumination - 4.7L AN/DN/DR vehicles.

2. While operating in speed control, a loss of vehicle speed may be experienced prior to transmission down shift. The up shift may then be noticeably delayed.

3. Selecting “OD-Off” may produce high engine speeds while operating with the transfer case in low range.

Service technicians are not required to duplicate these concerns. If the vehicle operator’s description matches the Symptom/Conditions or the vehicle exhibits any of the Symptom/Conditions, perform Repair Procedure.


Never look down on anyone unless you are helping them up - Jesse Jackson

 

[JPNinPA]

There also may be a bad transmission valve or solenoid if the oil is clean and the correct level.


Never look down on anyone unless you are helping them up - Jesse Jackson

 

[RobC100]

235 65/R17. Sorry for the delayed reply. Apparently I don't have my account set up to send me an email if I have a response.

 

[RobC100]

The PCM flash/reprogram might work, although if its a programming issue, why hasn't it been doing it all along? Any idea how much the dealer might charge to do it?

 

[RobC100]

Regarding the valve or solenoid, would I expect to see a DTC (fault code) with that, or could it happen without a code?

 

[RobC100]

Ok. I finally solved the problem. I tried checking exhaust back pressure at the upstream O2 sensor ports but consistently got around 1psi even at higher rpms. That ruled out the muffler and cat converters and breathing issues. Next I rented a fuel pressure test kit, plus since the Jeep has 95K miles on it, I went ahead and replaced the fuel filter/regulator first. When I read the pressures (prior to start, at idle and at 3-4K rpm) all readings were spot on. Took it out and it ran like a champ! It was simply a clogged fuel filter. Thanks again for everyone's input. Hopefully this thread will help someone else in the future.

 

[JPNinPA]

So the issue was the fuel pump not allowing the transmission to kick down??


Never look down on anyone unless you are helping them up - Jesse Jackson