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Reply To: Transmission Fluid 2002 Sienna

Slick One
Brandon Towne

My issue is the transmission calls for Dexron III in the owners manual and on the dipstick. This transmission was serviced at one point in its life by a Toyota dealership and they put in Toyota T-IV according to a service record.

I need to know if it is safe to do a drain/fill with the proper fluid Valvoline Dex/Merc even though the transmission as the incorrect fluid in it right now.

So is drain/fill fine because obviously during a drain/fill it is not getting out all of the old incorrect fluid that the dealership put in it during a service years ago but it will be diluted with fresh correct fluid.

Basically will Dexron III (Valvoline Dex/Merc) and the incorrect fluid Toyota put in it years ago Type-IV have bad interactions with each other or should I just pull the transmission cooler return line and do a complete flush?.