Dealership can't figure out what the heck is wrong with my Taco.

It turns out some of the FJ and 4Runner guys have experienced similar issues. The culprit is a faulty torque converter clutch which supplies the lockup function for overdrive. This explains why the issue does not occur in "4." The torque converter will need to be replaced to correct the condition.

As predicted, I started to suffer missed shifts/slipping after a short time. The Taco is now at a very well regarded AAMCO shop awaiting teardown. The good news is AAMCO will warranty the rebuild and new torque converter. I will update this thread with the results.

 

The shop is installing a used transmission and torque converter with 26,000 miles of use. This will cost $2700, and will come with a 27 month warranty.

 

Sounds like it's a 3rd gen.

 

These transmissions are typically pretty trouble free. I've heard of the A750 going over 700k without issues. The million mile tundra had the 4.7 V8 and an A750 transmission, it when to ~750k before it lost reverse and got rebuilt, then went another 250k to a total of 1 million miles without issues.
There is a screw on the valve body that you can adjust to make the TC lockup harder, if it were my transmission, the first thing I'd do is a valve body upgrade by IPT or a zip kit. Hopefully this transmission stays together. I'm at 80k and 10 years old, I might bypass the radiator cooler to avoid the pink milkshake myself, either that or replace the radiator. I'm also running a remote spin-on transmission filter in the cooler lines. I opted for a 3/4-16 thread filter head so I can use a napa 1269 hydraulic filter or the Toyota OEM

$54 90915-yzzd3 Oil Filter 1 Case (QTY 10)

90915-yzzd3 engine oil filter for the engine. There are a lot of other filters that will fit this head, it's a common filter size (PH8A)

 

Because y'all love pics... 4 years/20k on this filter and ATF, lots of short trips and towing. 80k total on transmission.

 

The filter in the pan is only good for something like 100 micron so just catches the boulders.. All the fine stuff goes right thru.

And this is why i have a magnefine in the return line from the cooler since it snags metalic down to 5 micron.
Keeping all those really fine metal particles away from those solenoids...

and before some one asks
1)The cooler line only dumps back into the pan, it doesn't supply pressure to operate anything in the transmission so any miniscule pressure drop due to the filter wont effect shifting.
2)The normal paper filter part has a bypass just in case it ever clogs up but i change these every 30,000 miles and there is never been anywhere near enough buildup of material at that point that would cause it to clog. If there was i think you have much bigger problems
3)yes there are magnets in the pan but they don't catch all this very fine stuff. If they did i would never find anything on the magnefine magnet and its always coated in stuff so fine you cant feel any abrasiveness if you rub it between your fingers. almost looks like silver paint.

Added benefit, when you do change the filter the magnets are great for sticking notes on your fridge

http://www.fourwheeler.com/how-to/t...atic-transmission-and-power-steering-filters/