Help - Disappearing Auto Transmission Fluid

We know he took it to a trans shop. We were wondering if he had first taken it to Jiffy for an oil change that they may well have screwed up causing his trans problem and subsequent to the trans shop and hadn't yet put that 2+2 together.

 

All great answers and you guys all covered the most common issues with fluid loss .
His transmission should be the A750 series . Engine load is controlled by the ecm now and drive by wire throttle position sensor . As mentioned above , In days gone by , modualtor valves were used to tell the transmission what kind of load was being placed on it . Modulator valves were famous for blowing . Ive changed thousands of them back when they were popular .

The only additional thing I can think of is the transmission overheating and fluid dumping out the vent line at the top of the transmission .
With this said , some guys route thier transmission vents up high to eliminate water intrusion ,but there would still be visual signs of a big leak with that much fluid missing out of the system . I agree with the guys here . He needs to consider another professional transmission shop with 5 quarts missing ?

 

So what separates the two separate components?

Hint. It's a loaded question, and I know the answer.

 

He has a 4x4, so it's an A750F... subbed for outcome.

 

If it had coolant in the atf I doubt it would have made it another 7,000 miles, usually the coolant will make the clutches come apart pretty quickly. Even if you get the transmission repeatedly flushed immediately afterwards they usually don't last too long. Occasionally you'll hear of them lasting a while after a pink milkshake, but not often.

If the transmission output shaft seal was leaking (common problem on the (4x2/prerunner) a750e), the transfer case input seal would also have to be leaking for the atf to get into the transfer case. I would think the atf would at least seep around the area where the transmission and transfer case mate together before it would start filling the transfer case with atf, not sure though. I think some vehicles actually have a weep hole to prevent the transfer case from filling with atf if there's a transmission output shaft leak or vice versa.

 

Exactly what I was thinking. There is a oil seal where the splines connect the two together

 

Not really the lip seal is only to keep the transfer fluid in it doesn't seal in both directions.

 

Wow. Lots of great ideas. Thanks guys!

I checked my coolant in the daytime and it looks clear and pink, but the upper half inch or so appears a little more clear (less pink). Does not look thick and milky to me. I will check underneath again tomorrow for any signs of leaks and be sure to check the undercarriage.

I haven't had my truck to a jiffy lube or anything like that in about two years. I normally do my own oil changes, and have not drained the transmission fluid accidentally (I would admit it if I had). The only work done on my truck has been since the problem first started. First, the Toyota dealer checked transmission and said they couldn't find a problem. Then the transmission shop (private, not aamco, etc.) twice found low fluid levels, but couldn't find a leak and "literally don't know where else to look".

 

Do you have any way to monitor the trans temps after you refill it? I wonder if it's running hot? I have heard of them boiling out of the breather tube when they overheat severely enough. Usually you can smell it and see where it's leaked out if that's the case though.