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GuyC
Dodge Dakota
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2/02/2008
19:10:13
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 Subject: Dropping out of OD?
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Message:
Yesterday (whilst driving through the Mojave Desert at 80mph) My 2002 5.9 ltr QuadCab suddenly started (what appeared to be) dropping a gear/out of OD for just a couple of seconds. When this happened the tachometer surged by approx 200 rpm. At first I thought it was because I was getting blown about by some serious winds, but it was still happening when I got to calmer weather. The problem seemed to be worse when going down hills.
Does anyone have any insights? Is this the Transmission, or maybe something else?
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Manny
Dodge Dakota
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2/02/2008
23:32:04
| RE: Dropping out of OD?
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Message:
Sounds normal. When the trans is under load, even slight uphill, it often unlocks the torque converter to use the torque multiplication available when the converter is unlocked. This also puts the engine at higher RPMs, where higher HP and torque numbers live. Normally more often at slower highway speeds 50 to 60 MPH, and only takes a good headwind or mild incline at those speeds.
When coasting, as when you're going down hill, the torque converter always unlocks until you press on the accelerator to maintain speed or to accelerate. Then the trans logic will lock up the torque converter again. My '04 Dakota does it, My wife's '00 Jeep grand Cherokee does it, My '98 Tacoma does it, and I used to have a '92 Ford Ranger that did it also.
Check your trans fluid. Level ground in Neutral with engine running and at operating temp. Might be a bit low. ATF+4.
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GuyC
Dodge Dakota
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2/03/2008
14:30:42
| RE: Dropping out of OD?
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Message:
Manny, thanks for the response. I will check the trans fluid (as soon as it stops raining here in CA)
I have had the truck for 5 years and am used to the normal operation that you described. What I experienced was definitely abnormal. Perhaps my description of the symptoms was lacking. The truck seemed to surge - almost as if it were pushing against something that suddenly gave way. At the same time there was a slight jolt that I took to be the dropping of a gear.
This was happening, as often as every 30 seconds, while cruising on the flat or going dowm hills with the accelerator being used. I was not coasting at the time. It did also happen going up hills, but not when accelerating. I have travelled the same route, in the same truck, with the same conditions, dozens and dozens of times and never had the truck react that way.
Thanks for the help,
Guy
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daddio
Dodge Dakota
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2/03/2008
14:35:20
| RE: Dropping out of OD?
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Message:
200 rpm is probably the TC unlocking. if it was dropping out of OD it would be more of an rpm jump than that.
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Manny
Dodge Dakota
JOIN HERE
2/03/2008
18:33:46
| RE: Dropping out of OD?
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Message:
Oh. That's different.
In addition to fluid level check, investigate for possible vacuum leak or Throttle Position Sensor problem.
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