My 69 hemi bird has a different Dana 60 taken from another bird with a blown hemi engine. We installed it in the middle 70’s, and I am sure that nobody opened it up since it was put in that car. My car has about 65,O00 miles and soon it will have more. Do you think it’s a good idea to change the Dana lube? The answer is obviously Yes! Well, I had to ask.

Yes I would change it and replace the gasket to get a look inside at the gears. Just regular 80-90 wt, with a bottle of Ford Motorsport friction modifier added.

Gus

Should have changed it years ago. Cheap Insurance.

Change it and add the posi additive along with 75 80Wt H.D. gear oil

Nah, why change it, does it go bad? Stick your finger in the hole to check the condition.

Are you kidding ME
It has been hot and cold multiple times and absorb moisture when cooling off (if I'm remembering my high school chemistry correctly oil, liquid petroleum grease and water heated up will make sulfuric acid when it cools down, not pure acid but minute amounts, correct?) and you think it doesn't go bad

That’s what the vent is for, now IF you start cooking oil to the flash point by all means change it. But then the oil is the least of the problem. My 65 Plym still has the original rear and trans fluid, still good.

I've only changed fluid once in a rear end in 45 years and have never had any problems. The 1 I that I changed the modifier had worn out and rear would stick & clank going around corners. Probably could have just added the modifier and been fine. Also I have never changed trans fluid in my regular driver trucks and cars and have never had a tranny problem but my friends who changed their fluid in the same models did.

I’ve been surprised at trans guides that state something is lifetime fill. I saw an old mopar service film that stated a 727 had lifetime fill fluid for normal service. I changed an NP435 one time where it had milkshake coming out. 22,000 mile truck that was 20 years old. I’m sure it was factory fill.

the go to additive at one time [at least around here] was the GM stuff.
some now recommend jeep brand additive.
what's the difference ? i don't have a clue.
what i do know, however, is that adding a container of the "strange" brand additive cures a sticky lock up converter clutch !
that worked perfectly in my wife's 94 concorde front drive transaxle.
i don't know where i heard about that, or who told me, but i couldn't believe how good it worked.
just my personal experience in life.
your results will vary.

Ok so now I got to know the brand and type for my Van!

I believe the oil does not wear out very quickly. 90 weight and Mopar additive is what I use. Putting 100K on an axle I would be looking inside of it because usually if it is Dana in a car it has been used well. So both Cuda and Cab are correct in their thinking. If you feel you need to change the oil do it. If I put another rearend in the a car I change the oild because I want to do it once, and take the cover off inspect everything pull axles check flange to flange. I have not check my Dana in my Challenger since the gear change in 1971 but it has only had maybe 600 miles put on it at the race track and I do not hear any noise or feel anything bad in the rear end. Me, I would take it apart look it over make it like new and forget about it for another 75K.

This is what I used that was recommended for clutch type and solved the sticking problem.

https://www.amazon.com/Genuine-GM-88900330-Lubricant-Additive/dp/B0028CMPIS

Condensation occurs when the outside weather drops the temps and humidity, a hot rear end makes heat and the breather lets out that hot air, once the car stops and sits overnight the rear end sucks in outside air through as it cools down, just like the motor and transmission does