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Discussion Starter · #1 ·
Somehow I engaged DAC and didn't realize it when backing up my boat up my very steep driveway. I realized afterwards and it didn't seem to be a problem at the time, but later in the day when my wife was driving without towing, after 30mph/50kmh it started doing a significant jolting/jerking which can only be described as coming from the transmission/drivetrain. She pulled over and I ran over in our other car to see what was up. It did it for me as well, so we limped over at a slow speed to the mechanic we use and then lo and behold, he took it out and up to 40mph and nothing. So weird.

We took it home, drove normally, and towards the end it started again. Pulled over, turned the car off. Started up again, continued the rest of the way - no problem. I took it out a third time on the highway and from a stop light really gave it gas and got it up over 70mph with no problems whatsoever, no transmission noise, no hesitation, no shaking.

Of course, I have no confidence in the car at the moment and am thoroughly in the dark.

For those who know the transmission and DAC, is it possible something got "bound up" which is now released, or is the transmission definitely in need of servicing?

2009 Highlander Sport AWD

Thanks!
 

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Discussion Starter · #2 ·
One quick note - I thought DAC worked through the transmission, but after reviewing the manual it says "The brake actuator may overheat", so obviously DAC is not in the transmission and perhaps the load was too great. (Boat is about 3200lbs all wet, and the Highlander can pull 5000lbs, but it is a very steep incline which I'm sure completely changes everything)
 

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Discussion Starter · #3 ·
Can anybody guess at what might cause that kind of intermittent repetitive shaking/jerking?
My wife has since drove it over an hour on the highway and no issues - it's so damn weird.
 

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If it was my vehicle....I would immediately stop driving it and have a qualified shop pull the codes and do whatever tests are needed. Transmissions can destroy themselves pretty quickly and that will be big bucks. Your latter posts seem to point toward the DAC not being involved so possibly something did get damaged, good luck.
 

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Call the dealer and speak to a service rep. It may have to be assessed by their mechanic as well. Anyone else is purely guessing. Could be a very costly guess!!
 

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Discussion Starter · #6 ·
Call the dealer and speak to a service rep. It may have to be assessed by their mechanic as well. Anyone else is purely guessing. Could be a very costly guess!!
I called the dealer and they don't do any tranny work, so I have an appointment next week at a transmission shop for them to pull codes and do a light inspection. Still so strange that the shaking has disappeared.
 

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I thought DAC is a controlled brake thing, Sort of like the ABS system. I doubt it has anything to do with the transmission except to lock it in the lowest gear.
 

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I have had problems with my DAC and snow buttons sticking in my 2013 because it is on the console pointing up and easily fills with crud. The dog sometimes accidentally steps on them.

You may want to check if the button is working properly- not stuck between position.
 
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