Transmission Fluid Flush

[sjonnie]

As I said, do 3 drain and fills at the same time if you don't do the Gibbons method.

Obviously that only works if you run the engine in between otherwise you'll just drain out the new fluid again. Overall, you'll replace about 75% of the old fluid and use about 9qts.

[Antherzoll]

Why not use the Valvoline Synthetic instead of the 3309?

Stephen

Now you've done it... You better duck your head.

[sjonnie]

Why not use the Valvoline Synthetic instead of the 3309?

You can use any oil that meets the JWS 3309 specification, several people have used other oils without a problem. In general, people have found they can buy Mobil 3309 or Toyota T-IV at less cost that other synthetic fluids, hence there doesn't appear to be any advantage to using different fluid. One reason to be wary is that manufacturers have been known to change the specs in an oil or even change what specifications the oil meets. Mobil 1 MultiVehicle Synthetic ATF is a prime example, Mobil claimed it met the JWS 3309 spec but then withdrew that claim at a later date.

[nelaco]

The concern DIYers have, myself included, is that they will screw something up. It's natural to worry that something you do will not work out how you intend, especially if it's something you're not familiar with. But the reality is, the transmission is designed to work with Mobil 3309 as it comes out of the bottle. That is, new fluid is perfect for the transmission, it is free of particulate matter and has the correct lubricant properties to ensure optimal functioning of the transmission. Old fluid is exactly that, old, worn out, contaminated and definitely not optimal. There is no benefit to running with old fluid or a mix of old fluid and new. Old fluid should be replaced, all of it, and the Volvo method does that in the best possible way by using the oil pump inside the transmission.

I once made this mistake. I replaced all of the fluid at once on a transmission with about 70k miles with original fluid. A month later and about 3k miles it failed on me. Had to get a new transmission. Nothing was wrong BEFORE I replaced the fluid. Obviously I had waited too long to do this. The new fluid dislodged a bunch of build-up and clogged the little passages. The idea of a drain & fill 3 times with 200+ miles in between is that only so much can get dislodged at a time with only 3 or so quarts of fluid being new. Plus, anything that did come off is being drained soon after.
After this is done at least 3 times, only then I would do a full flush.

[Astro14]

I once made this mistake. I replaced all of the fluid at once on a transmission with about 70k miles with original fluid. A month later and about 3k miles it failed on me. Had to get a new transmission. Nothing was wrong BEFORE I replaced the fluid. Obviously I had waited too long to do this. The new fluid dislodged a bunch of build-up and clogged the little passages. The idea of a drain & fill 3 times with 200+ miles in between is that only so much can get dislodged at a time with only 3 or so quarts of fluid being new. Plus, anything that did come off is being drained soon after.
After this is done at least 3 times, only then I would do a full flush.

I think you're confusing correlation with causality. The flush didn't cause the failure, even though it immediately preceded it. The wear already happened before the flush, and it was on its last legs anyway....