ATF fluid changes ARE Required.

probably have a chunk of crap stuck in the gasket breach since no knock for along time.

 

Just did the transmission fluid and motor oil at 100k miles. After reading all post and video, transmission fluid change seems not much difference than a motor oil change. The change part is easy. Most the time spent on jacking up the car, balance it, removing the plastic bottom cover, and remove the plug screws. My car only took 3 bottles before it spilled out. The end result is huge, car runs so much smoother, the biggest change is on coasting. The car can roll or coasting so much farther than before, the battery also seems to charge faster and last longer. Definitely worth the change. I will do it more again in the next 50k or 60k miles. At 100k milse, the fluid is pretty much black. Toyota should recommend it on their service manual.

 

I suggest you check the transaxle ATF again since the rated capacity is 3.6 US quarts. You do not want to run the transaxle with 0.6 quart of oil missing...

 

The refill capacity is 3.6 quarts according to the 2011 manual. Mine overflowed at about 3.3, which was slightly more than came out.

 

This is difficult to quantify. In an ideal world, we would run a series of roll-down tests before the oil change and compare to a set after the change. But given the relationship between viscosity and temperature, the lower friction losses would leave the oil cooler.

A better approach might be to:

• raise the car
• let it cool over night
• use a power drill to spin up a wheel to "n" rpm
• measure time to stop
• change transaxle oil - start engine to push new oil through transaxle
• use a power drill to spin up a wheel to "n" rpm
• measure time to stop

So we could use the relative stop times to estimate the drag reduction BUT we don't have hard numbers.

For hard numbers, we take a full-size equivalent tire and suspend it from a rope. Then we 'spin up' the tire and let it go and measure the resulting rpm at the maximum and change in altitude. The altitude change and tire weight over the altitude change gives us the potential energy. Now we have a metric for the polar moment of inertia that we can use to calculate the energy saved by changing the transaxle oil.

This is a bit of work but just the type of problem to give to undergraduate engineering students.

Bob Wilson

 

Yes, you are right. I was thinking about G2 Prius.

 

I put the old fluid into an empty 1 gal bottle. it filled about 3/4. so it's close to the 3 bottles ATF WS I put in. But I have the same worry, I will jack it up again this weekend and top it off a bit. I guess mine wasn't use the 3.6 because it wasn't complete cool down when I drain it, also a bit off balance.

But so far, car runs smoother and coasts better. I'm seeing 1-2 mpg gain for the same commute route.

 

One could or one could just change the fluids proactively because automotive fluids breakdown from use. If there is/was a noticeable difference, then it was in there too long already.

 

Funny, he says he "balanced" it, which I think he means got it level. Maybe not all came out? It was level,

I rechecked my level a few days after a change, the Repair Manual suggested to do this. But it hadn't changed at all, was still right at the lip. Next change I did, I didn't bother with a recheck.

It's a little puzzling that you only got about 3 quarts out, and replaced the same amount. Maybe the fluid was sold a cup or two hung up in there?? If you had the car level, and it started coming back out when you were filling, my money would be on everything's fine.

 

Car wasn't completely balance, the head was a little higher than the rear. So I guess some old liquid was still in there. But the drained liquid is close to the added amount. I'll balance it and top it off again, just to make sure. Thanks!

 

Ok, updating my guesses then:

You likely got a good drain. A little bit of tilt, one way or the other, doesn't matter: it'll still drain just fine. But the fill bolt is towards the rear of the car, so maybe with slight downslope, front to rear, it started coming back out a bit too soon as you filled. The spec is 3.5 US quarts though, so if you got 3.0 quarts in, you're a couple of cups shy. The spec also says anywhere between level with the fill hole lip, to 10 mm lower is fine.

I think when you raise it, and level more carefully, you'll maybe squeeze a bit more in, but not much. It's good for piece of mind though, that's what I did the first time, just to check, thinking it might somehow "settle". But it was still right at the fill hole lip.

 

Don't you wish there was an inexpensive and simple jack that could raise a car a few feet, without tires, and keep it level?

 

Floor jacking at the front and rear central jacking points, plus safety stands, works ok. Only thing, I use alternatives to the scissor jack lift points, inboard on chassis strong points.

 

When I changed the trans fluid, I pulled the can into a slanted driveway, facing downhill and then drove it up ramps until the car was level.

 

Come on, it sucks to slide under the car like that. I want to get it three or four feet high.

 

That's a great fast approach. But I always avoid to work on a sloped surface. I feel much safer on a level ground.

 

Piece of cake, I did it that way several times. If I change the trans fluid on the Volt, I'll probably do it the same way.

 

Being conversant in floor jack is good. Tire rotation for example: it's a bear on a sloping driveway with one end on ramps.