The way I look at the $5k figure keeps getting floated around for how much one of these tranny's cost, and after Gilly saying that if the fluid level isn't right you could cause damage. Also that you need special super expensive computer to give you a anccurite fluid temp reading. $300 every 100k seems cheap to me, I would just bring it to the dealer and not overthink it. Or don't change it just as many techs say change it as say don't worry about it.

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2006 CL500
2009 C300 4matic
1969 280SE
2023 Ram 1500
2007 Tiara 3200