Continuing the discussion from Car part discounts:
diy-full-flush-for-automatic-transmission
There are many, varied ways I’ve heard of doing a full fluid exchange (“flush”). Which one is the best method achievable without some fancy $10k machine?
Soliciting all comments…
Taking your transmission apart for a full rebuild would successfully be an entire fluid flush, and is the only way I would do it.
Service manual only calls for filter change every 100,000 miles and has the following info:
(a) If only fluid and filter were changed, start by adding 10 pints (5 quarts) of ATF +4 to transmission.
(b) If transmission was completely overhauled and the torque converter was replaced or drained, start by adding 24 pints (12 quarts) of ATF +4 to transmission.
The service manual never calls for a flush, as far as I know flush is some bullshit cheap transmission shops try to sell you. Fliters are for particulate, since there are no explosions inside your transmission, it doesn’t make sense that the fluid would severely degrade over time the same way engine oil does.
I’m not an expert, for me and my jeep I just follow the manual lol
This. While clutch material does slough off into the fluid, large enough particulates to cause scoring or damage to internal parts should be caught by the filter. Particles too small to be captured by the filter will dissolve into the fluid and increase its friction coefficient, maintaining the usability of the transmission for longer. Flushing this fluid out will leave you with slippery fluid flowing around clutches that have reduced friction material. It’s no bueno.
The fluid itself does degrade over time irrespective of clutch material or metal shavings, due to heat cycling and oxidation, but not nearly as rapidly or dramatically as engine oil. Generally, the filter change interval introduces enough new fluid, with enough frequency, to make oil degradation a nonissue.
If you’re seeing large amounts of particulates in your trans pan, you should consider rebuilding the transmission.
The only vehicles that had automatics that i’ve owned or cared to work on when I was a tech - came from the factory with drain plugs in the torque converter and the drain pans, so a filter and fluid change was just that-no special gear needed.
My F150 has a converter drain plug and the aftermarket pan has one as well.
The real question to ask those service garages that offer to sell you a transmission flush is - “does the flush include replacing the the filter as well?” The answer is usually no, we never replace the filter…I wonder if they every replace your oil filter, cabin air filter or engine air filter either - (if you don’t “need” the one "why would you need any?)
I don’t subscribe to the “auto trans flush” sales routine, or the “fuel,injection service” garbage either nor a host of other “specials” your service dept may offer to sell you…
Just buy a Grand Cherokee, they forget your cabin air filter from the factory!
I tried it on 6 separate occasions. Would not recommend.
If I did it again, I would buy a 1990’s Ford F-350 Diesel 4x4
On my drain plug AWOL '05 F150:
Disconnect ATF cooler return line.
Slide vinyl tubing over and secure with zip tie
Affix other end of tubing over 1 gal graduated plastic painters bucket.
With one person watching fluid, start truck, and run until fluid flow stutters, shut off quickly
Drop now mostly empty pan, and filter. Install new filter with extended pick up, and new extra deep finned cast Al pan
Add roughly 5 quarts of ATF, to roughly full level
Drain painters bucket, start truck, and run until 3 or 4 quarts in painters bucket.
Repeat until about 5 gal or ATF cycled through. On 3rd and 4th cycles, run through the gears manually.
Connect return line, and perform cold level check, then warm up and finalize fluid level.
My “flush”: do a regular drain and fill, drive it around however long makes you comfortable, do another regular drain and fill. Only “flush” I’d ever do. And even that’s only because I’m a little extra paranoid due to my tranny (automatic, I KNOW I KNOW I SUCK) not having a regular maintenance interval; it’s “lifetime fill.” As in, when your transmission dies from running fluid with a crapload of particulates and practically none of its additive package left, that’s the lifetime of the car. (And in case it needs saying: yes, you bet your happy arse that goes along with a filter change.)
