Auto transmissions fluid replacement schedule

[OregonBP9]

A quart of Amsoil ATF and a transmission bearing cost about the same, one is just easier to change than the other.

[phatvw]

Rather than doing a full transmission fluid replacement (~12 quarts) every 30,000 why not do a simple drain and fill every other oil change (3-4 quarts). That way you always have some new fluid in the system.

If you do oil changes every 4000 miles, then do the ATF every 8000. Which means the equivalent of a full fluid replacement every 24,000 miles. On average, the fluid is fresher throughout the lifetime of the car and the transmission will perform a lot better.

Drain and fill takes all of 15 minutes and you don't even need to jack up the car. Its actually easier than an oil change cause you don't need to do the filter.

[147_Grain]

Originally Posted by phatvw

Rather than doing a full transmission fluid replacement (~12 quarts) every 30,000 why not do a simple drain and fill every other oil change (3-4 quarts). That way you always have some new fluid in the system.

If you do oil changes every 4000 miles, then do the ATF every 8000. Which means the equivalent of a full fluid replacement every 24,000 miles. On average, the fluid is fresher throughout the lifetime of the car and the transmission will perform a lot better.

Drain and fill takes all of 15 minutes and you don't even need to jack up the car. Its actually easier than an oil change cause you don't need to do the filter.

I've been following the above advice for decades. Well said!

[OregonBP9]

Originally Posted by phatvw

Rather than doing a full transmission fluid replacement (~12 quarts) every 30,000 why not do a simple drain and fill every other oil change (3-4 quarts). That way you always have some new fluid in the system.

If you do oil changes every 4000 miles, then do the ATF every 8000. Which means the equivalent of a full fluid replacement every 24,000 miles. On average, the fluid is fresher throughout the lifetime of the car and the transmission will perform a lot better.

Drain and fill takes all of 15 minutes and you don't even need to jack up the car. Its actually easier than an oil change cause you don't need to do the filter.

That works great as a PM once you have a clean baseline. Most used vehicles don't and require a one time flush to completely purge the old. I use the trains pump method and let it flow tell 'clear'. Then I follow the OCIP intervals you suggest. Otherwise you're at best diluting dirty with 33% clean which is still too dirty for me.

[heyhar]

I did the first tranny service of our '04 at 30k, like the book suggested. I didn't like the darkness of it, so now it's the three or four quarts and filter every 20k. Stays nice and red now. Front wheel drive cars (which a normal Subie is until a wheel slips) tend to be harder on fluid than the rear wheel drive beasts we grew up with.

[mike552]

Originally Posted by heyhar

Front wheel drive cars (which a normal Subie is until a wheel slips)

[Xakepa]

I discussed that topic many times with numerous well-experienced technicians and the agreement was that if A)The liquid is still red and translucent (it is) and B) the liquid was not repeatedly (over)heated by towing, driving in hot weather, fully loaded uphills etc then probably I should not change it before 50K or so. Once at that point I intend to do "100%" flush thru the radiator tube, and be done with it.

For the diff oil, I was told, age is probably more important than miles - as long as it's clear 5 years service life is worst case.

Just my 2c - I live in temperate climate and seldom put much stain on the tranny