My car only has 25k on it. The additive for this fix is no longer available. Fluid/filter change is $600. I'm wondering if I can just get the fluid changed without the filter since i have such low mileage?

 

The additive is allegedly part of the fluid make up now.
How you can tell whether your new fluid has it or not is another question.

 

Can't say for sure, but maybe it isn't bad moment anyway to change the filter as well (I expect it not to be so expense), as some say lots wear material will happen from new (at least with the MB boxes). $600 is not cheap, what are they going to do for that ? Will the oil be fully flushed? Valid point from Norri, maybe someone knows from which date (fill date of the oil canisters) it should have the additive.

 

I agree, you can't change the filter without the fluid, so you would be facing another change eventually.
Do it all now and you should be good until close to 100K I don't think the filter/pan units are too expensive.

 

I wouldn't throw out my very expensive ATF at just 25,000 miles....

The ZF chirp or bark is just a nuisance. And it may go away. Ours did. Our ZF was barking occasionally in the late summer / early autumn of 2010. Deeper into autumn as the weather cooled off, the barking diminished and then ceased. Coming up on 70,000 miles on the car now. I'll begin considering an ATF drain-and-fill between 80,000 and 90,000 miles as long as our ZF electrical connector sleeve does not develop the dreaded leak....

 

I have one unopened bottle of additive. PM me if interested.