Re: To drain or not?

Posted by Tim Cole On 2014/7/19 18:05:33

There is a service bulletin for the Twin-Ultramatic recommending friction modifiers. They act to increase clutch engagement a few milliseconds to produce smoother shifts. These might help reduce the DD chatter.

I think a better use of your car would be to draw a sample from the trans and send it for analysis. Any diesel shop can do that for you.

If the color is good and the report is good the only reason to change it would be to switch to modern Dexron.

Whatever is in the pan is going to stay there. The recommended change interval is 25,000 miles. If the car has only gone 10,000 miles in the last 40 years there isn't much reason to change it.