Originally Posted By: Tones
Originally Posted By: Steelwheels
..Google JWS 3309 and see how it requires very specific modifiers (which in the past were not compatible with Dexron and vice versa) to allow for proper long life operation. I'm sure this all may have changed, but not betting my transmission on it at the moment.
Volvo has a TSB for older transmissions that recommends their new 3309-type fluid to solve some rough shifting problems. I don't know where you are getting that FM's are not compatible with Dex III. The transmissions may not require them, but that does not mean that the Dex III are not compatible with them. As I understand it, and granted I am not an expert, the 3309 fluid is pretty much backwardly compatible but the Dex III is not forwardly compatible (obviously). So it does make sense to formulate a fluid that would fulfill both roles.
I have seen the Volvo TSB before and remember it recommended the FM's. I must not have taken that TSB as stating that all DexronIII transmsissions are totally compatible with 3309 fluid. I've heard of different types of transmissions benefiting from adding FM's and just assumed that reading that TSB, this was the case. I had no idea they were saying it is good to run 3309 in all Dexron transmissions. I will have to go back and read where it said that.
I stand corrected. Good to know that it is fine to run 3309 in a Dexron transmission. Before I would use it that way, it would be nice to see a car or atx manufacturer that calls for Dexron say that it is fine to run JWS3309.
One would think the Mobil 3309 specs should state they meet the Dexron spec also. I don't think it does, but I might have missed that also.
A Mazda TSB Oct 13, 2004 warned strongly that 3309 was incompatible and should never be mixed with or topped off with Dexron. This is their words directly from the TSB "This new fluid is NOT compatible with any current fluids offered by Mazda such as (DexronII,III Mercon or Mercon 5. Any mixing of JWS3309 fluid with DexronII/III, Mercon or Mercon 5 will cause internal ATX damage and/or shifting concerns, even if just topping off the ATF during PDI." They were talking about putting Dexron in a 3309 ATX and we all know that is not good. But the severity of that warning has always made me not to want to mix them either way. I always assumed that since none of the original JWS3309 spec oils said it could be used as Dexron that it was not compatible that way either. Guess that is what I get for thinking, lol.
I'm no expert either and the emergence of all these multi-vehicle ATF's that meet the 3309 and Dexron specs look like there is alot of truth in the fact that 3309 will run fine in Dexron apps. Heck, they might have been the original multi-ATFS and just did not label it as such.