Transmission fluid

how important is it to have the transmission fluid flushed in your vehicle and what is the recommended time to do it?

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Short story - drop the pan & change the filter every 30K miles.

If you have the spin on filter, Subaru doesn’t recommend changing it until some other transmission work is required. Many change it at various intervals, not necessarily just 30K intervals. I do an ATF drain every 30K miles.

A drain and fill on this kind of transmission doesn’t require a pan drop, merely drain the ATF out. To get a higher increase of fresh fluid, I drain and fill 3.5 qts or so in two week or so intervals. This approach seems to restore the fluid well. Some folks do a third drain.

The other option is have the mechanic do a transmission fluid exchange, which will get a much higher percentage of clean fluid in the sump, and costs more. I will have this done when our Subaru reaches 150K miles.

We don’t recommend FLUSHING, and your OWNER’S MANUAL does not recommend it either. The manual will call for DRAINING the fluid and changing the filter every so often. Experienced posters here recommend you do this every 30,000 miles or so. That ensures maximum transmission life. Your owner’s manual may recommend a longer interval, but that’s a sales pitch to imply low maintenance.

If you tow a trailer, changing fluid and filter every 12,000 miles is recommended.

Flushing is a quick way for shops to make some profit. Flushing an old trnasmission that has not been serviced regularly will likely damage or destroy that transmission.

If you have not had your transmisssion serviced in the last 30,000 miles, do so now and have the fluid drained and filter chnaged by a reputable independent shop. If you live in a small town and there is no such shop, go to the dealer. Avoid trasnmission “chain” shops. They love to sell you a new (rebuilt) transmission.

Personally, I have been doing this since 1965 and have only spent $185 on transmission REPAIRS over that 45 year period.

If you want to prevent transmission problems, you should have the fluid changed (NOT flushed) every 3 yrs/30k miles, whichever comes first. The Subaru Maintenance Schedule calls for “inspection” of the fluid at those intervals, but unfortunately visual inspection will not reveal depletion of vital additives in the fluid.

I have always gone beyond Subaru’s “inspection” recommendation by changing the fluid at the 30k, 60k, 90k, 120k, and 150k service intervals, and I have never experienced any transmission problems with either of my Subarus.

Once you begin to experience trans problems, it is almost always too late to undo the problems with a fluid change. Prevention is what you need to do, rather than trying to play catch-up on maintenance once problems begin.

Thanks for the info