I found that syn atf made for a noisier (noticeable) trans.


I changed out the fluid at 12,000 miles post rebuild (Sun Valley) thinking I'd go 25k or more between filter/atf changes. Trans seemed to "whine" a bit in neutral, first, and reverse gears.


Got a little worried and changed the fluid back to dino atf. No more whine.


I double checked with Sun Valley Trans who reported that syn atf may result in increased trans noise but won't hurt it, and syn helps with heat dissipation.

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1986 300SDL 440,xxx