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General Dakota Board
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cbmoose
Dodge Dakota
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4/07/2009
19:45:20
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 Subject: Transmission control
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Message:
Currently driving a 2000 Durango 4X4 with the 4.7 engine and automatic. It's developed an issue with the converter clutch control, and I wonder if an engine sensor is the culprit. Here's what it does:
The converter clutch engages at 30 mph, not the 37.5 mph it used to.
If at speed on the highway, the slightest upgrade causes the converter to unlock and cycle. Engaging the cruise control makes it worse...unless I use premium gasoline. Then it acts as it should.
The trans shifts at its normal speeds, and has no other issues.
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JasonB
Dodge Dakota
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4/07/2009
20:25:39
| RE: Transmission control
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Have you replaced anything that would affect final drive ratio?
New oversize tires, stuff like that?
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cbmoose
Dodge Dakota
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4/08/2009
18:55:55
| RE: Transmission control
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No, everything is standard. What I DID notice is that if I disconnect the battery for five minutes to reset everything, the trans will operate normally for about 50 miles.
I don't know if this is related, but the idle is normally around 500 rpm. It increases after I reset the computer.
Another anomaly is that when in cruise control and climbing a slight grade, the tach will increase perhaps 200 rpm and return to normal, as if the converter clutch was "slipped" slightly.
Rich Ehrenburg said that he thought that perhaps my brake lamp switch was a bit hyperactive. This began last summer, and caused me to have to drive to Myrtle Beach without cruise control to avoid the "flickering".
When I told him that when I drove home without incident after using only premium gas, he didn't have an answer.
I've owned the truck for six years now, and it's never pinged on any gas, and it doesn't ping now. Yet it would appear that either an antiknock sensor or the MAP sensor input is commanding the converter clutch to do what it's doing. I'm on the verge of unplugging it, but that will set an error code and it will fail inspection.
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JasonB
Dodge Dakota
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4/08/2009
20:00:46
| RE: Transmission control
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If you have a scangauge ( http://www.scangauge.com/ ), or other OBDII scanner, or can borrow one, you can check things in real time.
*** IMPORTANT FIRST NOTE ***
If you or anyone else has used a spray cleaner of any kind on the throttle body to remove the usual deposits, I would definitely suspect that some of that liquid found its way into the throttle position sensor and is messing with the voltages.
That would cause me to put throttle position sensor 1st on the list.
If memory serves, the H.O version of the 4.7L engines has knock sensors and the standard versions does not. But that's for the Dakota, and I'm not absolutely certain about the Durango configuration. If you do have knock sensors, and if premium gas makes it run right, then there may be two possibilities: one of the knock sensors or one of your O2 sensors might be marginal, causing the computer to think the engine is under more load than it really is, which would make it prone to downshifting/converter unlocking. The throttle position sensor plays a major role in all this as well.
My next suspects would be the two temp sensors (Intake air temp and Coolant temp).
Then the MAP sensor.
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cbmoose
Dodge Dakota
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4/09/2009
22:01:38
| RE: Transmission control
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I think that a friend of mine has a scanning tool. I can ask tomorrow.
No, I've never sprayed anything into the throttle body, nor have I attempted to use any engine degreasers.
All gauges appear to read normal, so I'll have to get the scantool to diagnose any further.
Thanks for your assistance so far.
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