How can you tell if a car has had transmission fluid changed before?

Whenever I buy a used vehicle I just assume the transmission fluid has not been changed and I go ahead and swap it out. I think most of the general public forgoes preventative fluid changes aside from oil changes and most other fluids only get replaced or replenished with component replacement.
Pretty much.

Oil changes every 3000 miles and ignore every other fluid!
 

Honda ATF is chemistry very different than any fluid for a stepped gear automatic. I have yet to use a multi-vehicle fluid in a Honda that delivers the same shift characteristics as the Genuine Honda fluid.

The traditional Honda automatics , not the 9 speed ZF units they're using now, were pretty similar to manual transmissions right? As far as design and build.
 
I talked to my stepdad who owned the car and he said he's never had the transmission fluid replaced in the car. I'm surprised it's in as good a shape as it's in. But I watched a youtube video and it's very straight forward.

Jack up car and support car
Remove skid plate from under transmission
crack trans drain bolt
lower vehicle back down
remove drain bolt
fully drain trans
replace drain bolt AND crush washer and torque to 30 lb ft.
Refill with 2.5-2.75 quarts Honda DW1 ATF
Start car and run shifter through all gears and let engine warm up
turn off car and check fluid level
 
I never had any opinion whatsoever as I didn't have an auto until 2011. But I bought a used car in 2016, that was 10 years old and had 81k.

I went to the Japanese indie and they recommended a tranny drain/fill. I was on the fence so I researched online and I found ChrisFix's vlog to be informative. Basically yes, drain and fill if it's not burnt, but if burnt, leave it alone. Indie said zero chance of damaging my tranny by drain and fill at 81k. I watched and the fluid was black, not pink. Also sealed tranny (as they're called as Toyota product, but not really sealed).

What I never realized was 1 drain and fill leaves 55% old fluid. 2 was like 31%, and 3 was 19%. 3 was where conventional wisdom stops. So it should be done prior to being burnt since 20% of old fluid will remain. Unless you're like me (on this car) and I went 4 which brought it down to 11%. You get the idea. It will never be 0% old and diminishing returns. Tech always set aside fluid old for me to see, and it was always black.

Toyota WS is so expensive and it's not even synth. But they were saying don't use something else. Toyota in general is expensive for parts and service. Better to go with BMW which is cheaper for so many things :ROFLMAO:
 
I talked to my stepdad who owned the car and he said he's never had the transmission fluid replaced in the car. I'm surprised it's in as good a shape as it's in. But I watched a youtube video and it's very straight forward.

Jack up car and support car
Remove skid plate from under transmission
crack trans drain bolt
lower vehicle back down
remove drain bolt
fully drain trans
replace drain bolt AND crush washer and torque to 30 lb ft.
Refill with 2.5-2.75 quarts Honda DW1 ATF
Start car and run shifter through all gears and let engine warm up
turn off car and check fluid level
The total ATF capacity is around 9 or 10 quarts I think. I would just do an ATF drain and fill now and during the next 3 oil changes since it had not been changed before you bought it.
 
I have tried so many wrong atf fluids in my 02 honda as a test for shift feel. Dex6, dw1, type f etc. the transmission didn’t destroy itself like the internet said it would. The biggest difference i noticed between the dw1 and any other atf i tried is the smell and fluidity. The dw1 seems thinner. Also most normal atf smells sweet but new dw1 smells vicious. Like it will remove your nose hair. So clearly there is some difference in the honda fluid.
 
ATF is probably the most complex fluid in your vehicle, and provides both a hydraulic fluid function and a lubrication function.

The biggest difference I have seen when trying to find specs of different ATF's is the viscosity. Does a viscosity difference affect both hydraulic fluid performance and lubrication performance and by how much? I don't know - ask the design engineer for the trans, and if they actually tested it for different viscosities.

Anyone that tells you it provides better protection is guessing. I prefer to not guess myself, but many have without issue. YMMV :)
Engine oils have more and different additives. Luckily the transmission doesn't have to deal with byproducts of combustion.
 
I do a spill and fill with a vacuum hose once a year with Dexron VI on my Suburban and it easily stays a bright red in colour. If you ever see it looking a bit brownish it probably wasn’t changed. Also, seeing black specs would be enough for me to have a full pan drop done.
 
Last edited:
Whenever I buy a used vehicle I just assume the transmission fluid has not been changed and I go ahead and swap it out. I think most of the general public forgoes preventative fluid changes aside from oil changes and most other fluids only get replaced or replenished with component replacement.
^this
I also assume that a used car either had no prior service or that it was done with the cheapest (and potentially incorrect) fluid available. Either way, the old fluids must go. This way I am confident that the fluid is correct and th job was done right.

I even did this when I bought a car from my brother, and I knew all the maintenance that was done previously. Gotta start fresh!
 
I buy Honda DW-1 and Honda ps fluid only for my Honda's. DW-1 is about $10/qt and ps fluid is $4/20oz. btl. Like someone else said do a drain and fill now and then at the next 2 or 3 oil changes. Then do one every 30k miles, very easy to do.
 
Back
Top