Transmission fluid change interval

For what it’s worth, a long time friend of mine who has been in the independent transmission business for over 40 years recommends 30k miles servicing of automatics; the same as me.

He deals with them 6 days a week and has also stated that the majority of prematurely failed automatics he sees have a common trait; lack of regular fluid changes.

He has also stated that some of those disgruntled car owners with failed transmissions who swear the units have been serviced when given the bad news brings up another trait; never any records to back up the claim.

I personally don’t like the term “sealed transmission” because it often leads to poor maintenance habits

Despite the fact that the term is used even by dealers and manufacturers, it’s flat out wrong. If there’s fluid in it there’s a way to get it in and a way to get it out and a way to check it.

Differentials, transfer cases, and manual transmissions have been “sealed” this same way forever and no one seems to mind or complain about it. Why is that?

The term “sealed” is definitely a marketing term to describe the transmissions that no longer have a dipstick. I think there’s agreement that they are not “sealed”.

@MikeInNH With all due respect, are you 100% certain that your transmission is sealed?

Sealed in the sense that there’s no dip-stick…and the only way to check the fluid is the drain the fluid or drop the pan.

He deals with them 6 days a week and has also stated that the majority of prematurely failed automatics he sees have a common trait; lack of regular fluid changes.

That’s why I still get my fluid changed every 50k miles even though the fluid is a life-time fluid. Tranny fluid changes are cheap - transmissins are not.

I know I’ll get flack for this question, but I believe it’s relevant.

For the majority of vehicle owners who only keep their cars for less than 100K-150K miles (and they do not tow), why should they follow a strict 30k-50k trans fluid change schedule, or even change it at all - especially if it’s not even called for in their owner’s manual?

Many don’t…

But sometimes life throws your curves…Economy changes…you get laid off or your company goes bankrupt and now you have to keep that car you were going to sell because you can’t afford a new one. Would be nice to know the maintenance was kept up.

I tend to agree with JoeMario, but might compromise and do changes at 50k and 100k.
Although the fact that I have a CVT, which is new technology, may push me towards the 30k interval.

Mazda now uses a specialized synthetic transmission fluid that is very expensive. A fluid drain and fill is over $200. They do not recommend changing it at all. I disagree with them but I also disagree with all the people insisting on 30,000 or 50,000 mile fluid changes. Transmissions are not exposed to combustion contaminants like motor oil and superior fluid technology has made fluids that work effectively for 100,000 miles or more. Where we once changed motor oil at 3,000 miles (or less) we now routinely use intervals of 7,500 or more because of better oil and tighter engine tolerances. I do not believe that we need to continue using transmission fluid change intervals based on older transmissions and less advanced fluid technology.

Since I keep my vehicles forever I will replace the “lifetime” fluid in my Mazda transmission every 100,000 miles. I will surely let this board know if a transmission catastrophe occurs.

Would be nice if we could get a number out of the manufacturer… Yes, you could say anything over 100k they don’t worry about, but on the other hand, they do recommend timing belt changes at, for example, 105k (my last car), so they do sometimes think beyond 100k.

edit: but this is a futile argument. Yes, if you change fluids at 30k, you will have less transmission problems. But you can also truthfully say: If you change fluids at 10k, you will have less transmission problems. What you really want is the max interval that will get the transmission to 200k miles (or some other number) …