Hi, everyone,
Sorry to start another transmission fluid level thread, but I haven't been able to find a definitive answer to this, and it's bedeviling me.
Most advice here and in the repair manuals seems to say that the transmission fluid should be at or below the maximum mark on the dipstick with the transmission at a “normal operating temperature” of 80°C. Many of the posts here suggest that this can be attained by driving the car for 20 minutes or so on the freeway. But here are my questions:
- How can I be sure the transmission is really at 80°C when I check it (not just "pretty hot")?
- Does this specification allow for the transmission fluid to go above the max mark if the transmission is hotter than 80°C (e.g., could it get up to 100°C under hard or hot driving conditions? Even if the engine isn't that hot?)
- If so, what's the highest "safe" level for the fluid on the dipstick when the transmission is "really hot"?
Most of the time I’ve had the car, the transmission fluid reads about halfway between min and max on the dipstick after easy driving in the city for 10-20 minutes. With this amount of fluid, the transmission shifts reliably, but often with a solid “kick” as it shifts up around 20-25 mph. However, after heavier freeway driving (e.g., 30 minutes at 70-75 mph, on a warm day), the fluid reads about 1/4"-3/8” above the maximum mark. During a long, hot road trip with a bad radiator cap a couple of weeks ago, I removed 8-10 oz of transmission fluid to get it down closer to the max mark, but then as the day got hotter and the hills got steeper (engine temperature up to about 100°C), the level went back up to about 1/4" above full. I left it at this level, but then, once I was home and everything cooled down, the transmission seemed to shift later and less decisively. At that point, the fluid was about 1/8” above the tip of the dipstick when cold (maybe about 3.3 cm below the minimum mark). Even driving for 20 minutes uphill (on a cold day), it didn’t come back up to the maximum, so I added about 6 oz. of ATF, which I think brings me back to about where I started (and brings the performance back to where it started). Now, if I drive 30 minutes on the freeway at 70-75 mph, the fluid is up to about full+1/4”, but otherwise, it is usually between max and min.
So, the question is, is the fluid at the right level now, or should I take some out, so it _never_ goes above “max”? Also, if it’s too high now, is it likely that any damage has been done to the transmission by driving hard with 6-10 oz. of extra ATF, and possibly staying at that level for years (I don’t know how full the previous owner usually kept it)?
Thanks for your help!
Matthias