When to check transmission fluid

Me and my dad got into a disagreement on when to check transmission fluid. I said it needs to be checked after the car has been driven a while and it has warmed up and the car is running. My dad says that after you let the car warm up you can check it and it doesn’t need to have been driven.

Your dad is right. In most cases the engine does not have to be warmed up at all. I always run the transmission through drive and reverse a few seconds before going into park. The engine does need to be running however. Again…listen to your father. He’s knows what he’s talking about. Just read your owners manual.

If you’re talking about an automatic transmission, the transmission should be at normal operating temperature. That would require some driving. The owner’s manual should explain this.

Manual transmissions can be checked any time.

Not only does it depend on the transmission type, it also depends on the vehicle. Generally, yes, the vehicle should be at operating temperature, regardless of whether or not it has been driven. However, I have noticed the Toyota Sienna transmission dip stick has two range markings, one with “hot” and one with “cold.” Evidently, on the Sienna, you can check it while it is cold too.

The car is an automatic and a Dodge neon. I thought that for the transmission fluid to be warm required actually driving the car a bit.

That seems intuitive to me too, and some owner’s manuals say something like “after the car has been driven for at least 10 minutes.” I guess the best way to solve this dispute is to let it idle for 10 minutes, check the fluid, then drive it for 10 minutes and check it again. If you get the same reading both times, your dad wins. If you get different readings, you win.

Good idea. I did a little “Mythbusters” experiment a few years ago. I marked a quart of ambient temperature transmission fluid level in a 4 quart pan. When I heated it to 200 degrees the fluid did get thinner but it only increased in volume by about a hairs width. You can check the transmission fluid cold or hot. The difference is minimal. I do like to shift a couple of times to drive and reverse before putting the vehicle back in park. To further my argument…If you fill your transmission with ambient temperature transmission fluid from a container would you not be “overfilling” it when the tranny warmed up? Yes…but the fluid would only expand a minimal amount.

My Haynes manual for a 2005 Accord says that it should be driven to warm up the transmission. If you don’t want to do that, start the engine, let it idle, and move the transmission through all gears. I’ve noticed that if the car is cold, it appears that I’m a pint low. But if I check it after getting home, it looks like it’s full.

It has been my experience that I have never had a tranmission dipstick that indicated an accurate/definite level line, and I am referring to probably 12 (or more) different vehicles, especially after adding fluid with a “drain & refill”. But it must not be too significant, as I have never had a transmission problem/failure. I have always tried to replace the same amount that I drained. My point being that checking it warm, after driving, cold, etc. isn’t that critical.

Chrysler has been very specific about temp for years when checking transmission fluid . The owners manual says to drive 7 to 10 mile and then check. when I have done that it usually reads between a pint and a quart lower when cold.