How often to change ATF on a street car?

100% stock cars were rated in the book for what, 100K miles? What about the typical C6 with extra clutches and a shift kit? I've heard WIDE ranges of times from yearly, even if the car is parked, to 10K miles, 50K miles.. What is a good timeframe?

I do the SWMBOs 3 every 15K, mainly because two of them are weekend toys, and sit a lot.
Her daily gets a lot of use, and $3500 for a rebuild on it is more than I want to spend...

The 100k miles is based on the fluid never getting hot and the the filter being able to do its job. When the fluid is cooled in the motors radiator and the motor over heats, it also over heats the trans fluid. Keep these things in mind as to when to change the fluid.

We have a Tranny builder here in Ohio that WILL, prove to you that IF, your tranny fluid is not burned ,your tranny's life WILL be longer IF you DON'T change it. New fluid in old seals SHE says ,is a nono.(Excessive expansion). I have 189k on my 95 GT and have never even changed the filter. But, its never been abused either.

With conventional atf, every 3 years or 30,000 miles, syn can go longer.

As far as leaving it in forever unless there is an issue, I dont buy that.....been building them too long and I can tell you more harm comes from not changing it rather than regular service.

My favorite is the one where a tranny has many miles on it and never beeen serviced, then right after they do the tranny takes a dump...............more like underlying issues.

I'll keep fresh fluid in all my trannys, ya'll can do what you want lol.

Ford motor co sends out service reminders to maintain your warranty , service at 30k miles-fluid and filter. At the cost of a trans its cheap insurance to change it.

bbf-falcon wrote:We have a Tranny builder here in Ohio that WILL, prove to you that IF, your tranny fluid is not burned ,your tranny's life WILL be longer IF you DON'T change it. New fluid in old seals SHE says ,is a nono.(Excessive expansion). I have 189k on my 95 GT and have never even changed the filter. But, its never been abused either.

Okay, as soon as you get to 300K miles on the original transmission, you let me know... I'm just about there on my '86 F150,
which I bought new from Kirkland Ford in '86, and it has an AOD in it... And my wifes '72 Capri, that has a BW35 in it, has just over
300K miles on the original transmission.

So I'll have to believe your tranny expert has a cranial rectal inversion problem...