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Anyone have any experience troubleshooting an AW55-50/51SN Transmission? Issue is transmission sounds like it is building up high pressure when at a stop but in drive. It's almost like the torque converter is trying to make the car move more so than it should. Makes whole car rumble. As soon as car starts to roll, pressure settles right down and rumble is gone. Shifts are mostly smooth. Slight surge when shifting from 1->2 and bump when downshifting from 2->1. I have tried a relearn procedure through VIDA and that made no difference. Do I need to adjust main solenoids in valve body? Or should I just replace them with Rostra, or Replace whole valve body or replace whole transmission? Thanks for any help or ideas you can come up with.
 

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I'm going to guess valve body.

I am friends with a guy who rebuilds transmissions for a living. He bought a 2000 S70 for cheap with intention to flip it in spite of my insisting that old S70 is a better car than his 2015 Ford Focus daily driver. He rebuilt the transmission (found a broken steel in the clutch pack) a drove it. Still shifts hard even after resetting adaptations. He concluded it needs a new valve body but for cost reasons, isn't going to do it.

With 170k miles on your S40, it kind of makes sense to put a reman transmission in it.
 

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I've used rostra the solenoids in my V50 with the AW55-50.
The main issue I had was a harsh downshift when coming down to a stop. This only happened when the transmission was fully warmed up.
Note that the solenoids did solve the harsh downshift (they were sticky), but I do notice a slight surge on upshifts. This is a minor issue and I will continue to drive the car as-is for a while.

If I had to do it again, I'd probably drill the VB cover and fit 3x of those "transmission drain plug" kits you can buy online, so I could tune the solenoids afterwards.

Or even better: remove the VB, Fit a Sonnax "Zip Kit", a set of their rebuilt solenoids, and a gasket set (VB has no gaskets from factory).

Finally, note that solenoid calibration is something you do after working on the valve body. It's no use to tinker with them on a VB that is already acting up.
 
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