Jiffy Lube With Penzoil Atf--did I Screw Up?

[topichka]

Hello All,

I have an 01 GS430--runs great and has 123K on her. I purchased the car with 56K on her and have done the 60K service, timing belt/water pump change, as well as oil changes at 5k miles. At 88K miles, I took it to Jiffy Lube to have the transmission fliud changed as I didn't know what the previous owner had done. Jiffy lube put in Penzoil ATF. THIS WAS BEFORE I READ THIS FORUM!

So, my quesiton is what to do now. I know, from reading this forum, that I should be using Toyota IV only. The cars still shifts nice and smooth but I'm trying to keep this car running a long time. Should I drain out the old fluid and replace it with Type IV? Should I do it gradually, drain and refill over a period of time or do a complete flush? Or, should I just let her be since everything still runs well and shows no signs of impending danger?

Much thanks!