What is this I heard that if you have a high mileage car, changing your tranny fluid might make it worst?

https://my350z.com/forum/maintenance...ml#post8020052

I have an 03 with an 06 transmission but my 5th is starting to get some grinds (coming from 4th) I was thinking of going fully synthetic to help the tranny a bit. (but i'm sure that wouldn't really do much difference) Then again, I just don't want to make it worst than before.

Can anyone tell me the legitimacy of that claim?

 

For auto transmissions it can be true but no always. For manual no. If you are having grinding noise I doubt you have an auto tranny. Try changing the fluid to some good redline, motul or anything comparable. The Motul 90pa would be the best choice.

 

Thanks! Yes, I have a 6MT.

 

No prob. If you need any prices on any of the fluid let me know.