TCC lockup question
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Professional
Joined: Mar 2010
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From: Orlando, FL
TCC lockup question
Hey guys,
I wanted to know if there is a PCM flash update for TCC lockup speed. The reason why I ask my 1995 3.9 locks up at around 47-50 MPH. I've owned 4 other Chrysler vehicles and all of them have locked up at around 40 MPH; my 1995 Grand Cherokee 5.2 V8 4x4 locks up at 35 MPH if I turn off overdrive. Thanks again in advance.
I wanted to know if there is a PCM flash update for TCC lockup speed. The reason why I ask my 1995 3.9 locks up at around 47-50 MPH. I've owned 4 other Chrysler vehicles and all of them have locked up at around 40 MPH; my 1995 Grand Cherokee 5.2 V8 4x4 locks up at 35 MPH if I turn off overdrive. Thanks again in advance.
Champion
Joined: May 2008
Posts: 4,839
Likes: 5
From: Apex, NC
To answer your question about the flash update... I have no idea. I'm not aware of any flash updates at all. That is something you would be much better off calling your local Dodge dealership and asking. Maybe someone on here will have an answer for you, but we're just a bunch of enthusiasts, not Dodge technicians.
Now, about what your truck is doing... This is what the 1995 Dakota FSM says about how the torque converter is supposed to work per factory spec:
Now, about what your truck is doing... This is what the 1995 Dakota FSM says about how the torque converter is supposed to work per factory spec:
TORQUE CONVERTER
...
Clutch engagement is controlled by the converter
clutch valve. The valve is located in the transmission
valve body. Clutch engagement occurs in drive range at
speeds above approximately 72-80 km/h (45-50 mph).
...
Clutch engagement is controlled by the converter
clutch valve. The valve is located in the transmission
valve body. Clutch engagement occurs in drive range at
speeds above approximately 72-80 km/h (45-50 mph).
CONVERTER CLUTCH CONTROL
The converter clutch valve applies the converter
clutch when supplied with line pressure through the
converter clutch solenoid. The solenoid is mounted on
the valve body and energized by an electrical signal
from the powertrain control module. Electronic control
of converter clutch operation includes clutch release
at closed throttle, during warmup, and during
part throttle acceleration. The boost valve provides
additional apply pressure for converter clutch application.
The switch valve directs fluid apply pressure to the
converter clutch in one position and releases it in the
opposite position. It also directs oil to the cooling and
lube circuits. The switch valve regulates oil pressure
to the torque converter by limiting maximum oil
pressure to 130 psi.
Converter clutch engagement in overdrive fourth
gear is controlled by sensor inputs to the powertrain
control module. In third gear above 25 mph and in
fourth gear above 50 mph, sensor inputs to the control
module that determine clutch engagement and
shift timing are:
> coolant temperature (verifies temperature minimum
of 60° F)
> engine speed
> vehicle speed
> throttle position
> manifold vacuum (MAP sensor)
The converter clutch valve applies the converter
clutch when supplied with line pressure through the
converter clutch solenoid. The solenoid is mounted on
the valve body and energized by an electrical signal
from the powertrain control module. Electronic control
of converter clutch operation includes clutch release
at closed throttle, during warmup, and during
part throttle acceleration. The boost valve provides
additional apply pressure for converter clutch application.
The switch valve directs fluid apply pressure to the
converter clutch in one position and releases it in the
opposite position. It also directs oil to the cooling and
lube circuits. The switch valve regulates oil pressure
to the torque converter by limiting maximum oil
pressure to 130 psi.
Converter clutch engagement in overdrive fourth
gear is controlled by sensor inputs to the powertrain
control module. In third gear above 25 mph and in
fourth gear above 50 mph, sensor inputs to the control
module that determine clutch engagement and
shift timing are:
> coolant temperature (verifies temperature minimum
of 60° F)
> engine speed
> vehicle speed
> throttle position
> manifold vacuum (MAP sensor)
So according to all that, yours is locking up as it should in overdrive. But is yours not locking up at all in 3rd gear? If not, its supposed to, and you likely have another problem on your hands.
Last edited by 95_318SLT; Apr 22, 2010 at 07:46 PM.
Thread Starter
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Professional
Joined: Mar 2010
Posts: 241
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From: Orlando, FL
yeah, it will lock up in 3rd gear like it's supposed to, but not below 47 MPH, so if it ain't broke, I won't worry about it. Just trying to save as much as I can on fuel now that it's creeping up to the magical $3.00/gallon. I need to replace my coolant temp sensor for the PCM because when the outside temperature is below 70, it takes a long time for it to lock up (over 45 min of driving).
Champion
Joined: May 2008
Posts: 4,839
Likes: 5
From: Apex, NC
Yeah, like I said, you probably have another problem besides the computer's flash. Replacing that ECT sensor might just get your TCC to lock up when it should!
In that last quote on my first post, theres a list of the sensors that the computer uses to determine if its ok to lock up the TCC. The ECT sensor was on that list, but if that doesn't fix it, you could run tests on the other sensors on that list.
The FSM gives simple tests you can do with a digital multimeter. You can download the '95 FSM for free... the link is on the faq page.
Its been over a year since my truck had an automatic transmission in it, but if I remember right, the TCC locked up around 35 mph in 3rd if I was just cruising. Maybe someone else who currently has an auto in their truck can verify that.
In that last quote on my first post, theres a list of the sensors that the computer uses to determine if its ok to lock up the TCC. The ECT sensor was on that list, but if that doesn't fix it, you could run tests on the other sensors on that list.
The FSM gives simple tests you can do with a digital multimeter. You can download the '95 FSM for free... the link is on the faq page.
Its been over a year since my truck had an automatic transmission in it, but if I remember right, the TCC locked up around 35 mph in 3rd if I was just cruising. Maybe someone else who currently has an auto in their truck can verify that.
mine never locked up untill about 60!. i know its not where it shoud have been since it was blown and still blowing ricers off the road but before it blew i took it up to upper michigan(210m from where i live) and it locked up around 45. then i decided to hit 100mph, after that she was never the same
Thread Starter
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Professional
Joined: Mar 2010
Posts: 241
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From: Orlando, FL
well, I replaced my coolant temp sensor ($12.99 @ autozone) and everything works as it should. Now my only problem I have now, I have to replace my windshield wiper transmission assembly. We had a wicked storm last night here in Orlando & thank goodness I had rain-x on my windshield or I would have been screwed.
Champion
Joined: May 2008
Posts: 4,839
Likes: 5
From: Apex, NC
