Last summer, we took our Corolla to a family friend mechanic who did a drain and fill tranny change. A few weeks ago, we took the same car to a different mechanic for a required inspection for our car registration. Our transmission fluid got flagged as burnt. We’ve put less than 5k miles in between the supposed tranny change and the inspection. Did we get taken by this guy and he didn’t change our tranny fluid, or is there something else going on with our transmission?
Right sample is the fluid in our car. Left sample is brand new Toyota tranny fluid (just in case that’s not obvious).
Doing a drain and fill on that transmission will replace about 1/3 of the fluid that the transmission holds. Once fluid is dark the best way to replace it is to do a transmission fluid exchange.
You can drain and fill the transmission three times (driving it in between drains) and get the fluid looking better but even that isn’t a complete service because you’re mixing the new fluid with the old.
The reason is probably as described above, the fluid prior to the transmission service was in pretty bad shape. The service drained out 1/3 and replaced that w/ 1/3 new, leaving a mixture of 1/3 new and 2/3 old. 5 K miles later it’s all mixed together, and not looking that new, as would be expected. The fluid now doesn’t look horrible, but it does look like it needs renewing. One idea, ask the mechanic who did it the first time to do it again.
Also good idea to double-check the mechanic is using the correct transmission fluid, the one that Toyota recommends for that year of Corolla.
Thank you all so much for your help. That totally makes sense. I’m a completely a car novice so I appreciate the explanations.
We bought the fluid from the dealership (Toyota ATF Type-1V I believe) so hopefully what was what he used.
Going forward, what’s the best service? I’m assuming I will have to do at least a few drain and fills? A total fluid exhange? Sorry if I’m not using the correct terms
The transmission fluid exchange machine replaces 100% of the transmission fluid.
So once you know the total capacity of the transmission, you fill the machine with the correct tranny fluid, start the engine, and let the pump within the transmission exchange the fluid.
besides, I’m not sure only 1/3 is getting drained, probably better to check on Toyota forums how much fluid Corolla or particular model year drains
for example, on Nissans I was working on, more than 50% get drained with a simple drain plug bolt, so 2 drain&fill operations result in under 25% of old fluid still circulating in the system
That fluid color is normal for an older vehicle that has only had a drain and fill, the fluid is aged and discolored, not “burned”.
I believe it is inappropriate for an inspector to be able to fail a vehicle during a safety inspection because of the color of the transmission fluid. Your transmission dipstick likely states that under normal operating conditions no maintenance is needed. Why should an inspector be able to decide that the fluid should stay pink? Manufacturers state that the dye in modern transmission fluid is not permanent and darkening is normal.
Honda said to never use a machine to exchange trans fluid, but to use the three drain/fill method. That was for my old 2005 Accord with automatic. What changed to make this OK, or is the same warning in effect for some cars?
Honda states that if the transmission is properly maintained, there’s no benefit to using a fluid exchange machine.
But if the transmission hasn’t been properly maintained, and a fluid exchange machine is going to be used, do not use any solvents, cleansers, or conditioners during the fluid exchange.
