Re: Trans fluid change: What else to do?

Posted by Tim Cole On 2012/5/1 17:11:47

"Life of the car" for transmission fluid means there is no required service interval. Just like sealed suspension parts and differential oil. The only time the fluid requires replacement is when the transmission is replaced.

But the manual for my modern car does list a service interval for towing and severe driving with high oil temperatues as per mountainous regions.

One thing about transmission oil is the additive "packages" keep changing. If an old transmission has good oil the clutches have been soaking in that oil.

I found with a couple of cases with cars taken out of long term storage that changing the oil in the transmission was not the thing to do. These were manual transmissions and they just didn't shift as well no matter what I tried. Even the exact oil specified by the original manual. Maybe the transmission and oil were both shot, but given new parts are not available in those cases fooling with the oil was a mistake.

Getting back on the original subject if an Ultramatic is having an intermittent direct drive lockup problem I think that switching to Type F might be the way to go. Supposedly Type F will run higher pressures than Dexron. Packard did specify friction modifiers in a 1956 TSB, but I think that was to address synchronous shift problems in Drive range.

Eventually these transmissions are going to need soft part modifications to compensate for worn surfaces the same way as a modern car.