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Old Aug 24, 2019 | 06:00 PM
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nxtdiesel
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Transmission question

I noticed when I'm accelerating and the truck is in third year that the RPM will drop slightly, maybe 200 RPM or so as the truck continues to accelerate.What causes that? Shouldn't the RPM continue to climb until it shifts into fourth gear?
 
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Old Aug 24, 2019 | 07:47 PM
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Guessing you are seeing the torque converter locking up.
 
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Old Aug 24, 2019 | 08:17 PM
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nxtdiesel
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Originally Posted by UGA33
Guessing you are seeing the torque converter locking up.
Will it lock up while accelerating like that? I thought it locked after you were at more of a constant load. Because the rpms were climbing then it dropped the 200 rpm or so and then the rpms started climbing again like normal, then it shifted to 4th.
 
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Old Aug 24, 2019 | 08:36 PM
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Originally Posted by nxtdiesel
Will it lock up while accelerating like that? I thought it locked after you were at more of a constant load. Because the rpms were climbing then it dropped the 200 rpm or so and then the rpms started climbing again like normal, then it shifted to 4th.
Yes. That is it locking in third.
 
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Old Aug 24, 2019 | 09:21 PM
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Originally Posted by nxtdiesel
Will it lock up while accelerating like that?
Yes, it will lock while accelerating.

After you reach a certain RPM the torque converter is no longer multiplying torque. It's slipping because the converter clutch is unlocked. Locking the clutch in this case will provide more torque to the wheels, less heat into the transmission, and better fuel economy. That's why it locks at that point.
 
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Old Aug 24, 2019 | 10:37 PM
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Sounds good, Thanks for the help guys.
 
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