If you have the 5 speed autobox, those are prone to break early. The software Volvo provided did not match the engine torque, along with problems with gear release timing.

The 4 speed auto was much more robust. With ATF flush every 100K Km, it usually lasts quite a long time. The solenoids can get dirty, but they can be replaced.

I would look for a donor/used transmission. Still, not a cheap option as the labor costs to replace approach 8 hours of shop time.

BTW, Volvo does not supply 'new' transmissions. They have 'refurbished' models for unreasonable prices.

Rule of thumb in the USA, do not buy a 2001-2 Volvo with automatic (our model years are typically 1 year behind the rest of the world). Holds true for the S80, S60 also.
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Keeping it running is better than buying new