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2016 Sealed Transmission Problem

2571 Views 6 Replies 4 Participants Last post by  Jack Daniels
2016 Rav4, gasoline base model with AWD and automatic 6-speed sealed transmission. 298k miles.

Operated normally at highway speed (70mph) until a stop at a rest area. Car was not shut off or put in park for the roughly 3 minute stop.

While accelerating back to freeway speed, the transmission seemed to "miss its shift" from 4th to 5th gear, allowing the engine to free rev. After a 2-3 second count, the transmission "caught" and accelerated normally to the 5th to 6th gear change, where it again missed the shift, free revved, and caught again after 2-3 seconds.

At top gear cruise, even at much lower speeds (40mph?), there is a transmission "pulse" or a felt "power surge", accompanied by a fluctuating rpm, as indicated by the tachometer.

I assumed a low fluid situation. Transmission was brought to recommended operating temp (104-113 degrees) and pan drain plug removed. 30 ounces of a very dirty, not quite black, trans fluid came out. Overflow tube (it's green) appeared to be in place within the pan drain hole. A little over 30 (31?) ounces of new fluid was added.

Test drive afterwards yields same condition, except that the "surge/pulse" isn't as hard.

When brought up to operating temp and engine off, and the transmission filled to its proper level, should there be any fluid that comes out of the overflow tube?

If I were to do a full transmission flush and fill, dropping the pan, how much trans fluid does the system hold?

Can the condition be fixed easily? Is it over full? (Car was supposedly fleet maintained. Although the condition of the fluid indicates that it wasn't changed.) Can reducing the amount of fluid, until it doesn't run out of the overflow tube, help the situation? Or will it hurt?

Worst case scenario, how much does will a replacement transmission run me, for parts and labor?

Have you experienced anything like this?
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There are a couple of videos on this topic - I know the Car Care Nut has one that goes through the AFT change procedure. At proper level / temp, the overflow tube should just drip out as that level is basically the height of the tube. I'm sure there is a spec somewhere, but since a fluid change is most common, most places suggest measuring what comes out and putting in just a tad more so it can be measured with the overflow tube.

298K is pretty good for what is probably factory fluid. One of my pet peeves are manufacturers that claim "lifetime" fluids. New Briggs/Stratton engines claim "never change the oil - just add to full". OK - I guess you're already planning on what mower you're buying next lol.
This link may help you out. I just did two drain and fills a week apart.

When brought up to operating temp and engine off, and the transmission filled to its proper level, should there be any fluid that comes out of the overflow tube?
there must be some fluid running out to confirm that the level is at the top of the overflow tube.
If nothing comes out, then the level is unknown.
Overfilling is best, then let it run out until only a trickle remains.

some other brands of car specify that to just check the level, a half quart must first be added, then check the level same way as Toyota prescribes, with out actually witnessing the overflow reducing to a trickle it could be easy to mistake the level.
So from what I'm understanding, my transmission was OVERFULL by about a quart!

I had 30 ounces come out of the overflow, as soon as I took the drain plug out.

Would the conditions I experienced be caused by an overfilling? I'm having trouble believing that, as I've put about 60k trouble-free miles on the car myself before this happened.
Though I do not doubt that the density of ATF is temperature dependent, I suspect your measure of "operating temp" is close enough... Toyota and others make a really big deal out of the exact temperature this measurement is supposed to be made, and it's a very narrow window.

I'm no expert, but I've been around the block. Overfilling can cause issues, but if it's been driving fine for 60K, I really doubt one day was one day too many and blamm. Personally, at 298K, I think you've got plain old wear and tear, exacerbated by possibly very old fluid.

I'm also of the camp that a power "flush" tends to do more harm than good. At this point, I'd just replace the fluid and use one of those "magic" liquid fixit chemicals that claim to help... See how that goes, and if not any better do another fluid swap and "fix". After that, start getting some professional opinions.

Good luck!
So from what I'm understanding, my transmission was OVERFULL by about a quart!
there may be a heat exchanger, with coolant from the engine in one side and transmission fluid in the other. If this corrodes internally the 2 fluids will mix, and most likely wreak your transmission first.
Be sure that any oil drained appears coolant free.

was the plastic fill level tube screwed all the way up?
The Toyota fill procedure specifies to confirm this is tightly up prior to a fluid level check.

Since the fluid was near black, it would be worthwhile draining it all and re-filling. Then drive a while and repeat.
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