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Understanding the AW 55-50 Neutral Control

A 2001 Volvo S60 come into or shop with a smoked AW 55-50 transmission that needed to be replaced.

The AW 55-50 transmission has a feature that Volvo calls “Neutral Control.” What is “Neutral Control” and what is its function? To tell you the truth, I wasn’t really sure, but below is what I was able to both find and figure out about it.

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Understanding the AW 55-50 Neutral Control

R&R Tech

Subject: The Neutral Control function and shift adaptation
Unit: AW 55-50
Vehicle Application: 2001 Volvo S60
Essential Reading: Rebuilder, Diagnostician, R & R
Author: Jerry Hunter

R&R Tech

  • Subject: The Neutral Control function and shift adaptation
  • Unit: AW 55-50
  • Vehicle Application: 2001 Volvo S60
  • Essential Reading: Rebuilder, Diagnostician, R & R
  • Author: Jerry Hunter

A 2001 Volvo S60 come into or shop with a smoked AW 55-50 transmission that needed to be replaced.

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The AW 55-50 transmission has a feature that Volvo calls “Neutral Control.” What is “Neutral Control” and what is its function? To tell you the truth, I wasn’t really sure, but below is what I was able to both find and figure out about it.

When the vehicle comes to a complete stop in drive with the driver’s foot on the brake, the TCM waits two seconds before disengaging drive or shifting the transmission into neutral. This feature is designed to reduce emissions and to minimize any idle vibrations. Releasing the brake pedal re-engages drive. This is a very smooth and seamless process that the operator never feels.

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However, when replacing the transmission, you must pay special attention and follow specific directions to adapt the new unit to the car. If adaptation is not completed properly, the driver will feel a very noticeable “thud” shortly after the vehicle comes to a complete stop. When the brake pedal is released, a harsh engagement also will occur.

Volvo has published a technical-service bulletin (TSB 43-38) that requires the use of its VADIS to put the car into adaptation mode. Once this tool is hooked into the system, you can begin the adaptive learn and test drive.

After the transmission is in adaptive mode, the orange triangle in the center of the instrument cluster will flash just after a perfect shift is obtained. Volvo considers a perfect shift one during which the TCM has reached its adaptation target for that particular shift. With the transmission in adaptive mode, you will experience all the types of shifts listed in the TSB until the light flashes to tell you it was a perfect shift. When all the shifts are perfect you are finished; the adaptation is complete.

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Does it sound as if this might take a while? Yes, it does!

I understand that the last Snap-On scan-tool update (11.2) included the updated software for the Volvo. Does anyone out there have the 11.2 update, and can you tell us whether it has the Volvo adaptation mode or we need to take this one to a Volvo dealer to have adaptation relearn done?

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