Piston Slap: Byzantine Transmissions in Frozen Highlands

Sajeev Mehta
by Sajeev Mehta
piston slap byzantine transmissions in frozen highlands

Mehran writes:

Greetings to you Sajeev and your evil twin Sanjeev, (yeah he’s dead to me – SM)

First of all thank you very much for answering my other question, just to give you an update on that, I ended up not buying the extended warranty. Now we recently bought a 2012 Toyota Highlander Limited to replace my wife’s old car(V6, 5 Speed automatic with the towing package which adds the trans cooler) it has 34K miles and this one has the extended warranty (100K or 2019). The issue that we have with the car is as follow, after a cold start (in the morning) if I put it in any gear (D or R) something funny happens, the transmission acts funny, it goes in and out of the gear couple of times. For example if I want to back-out of the garage when I put in R and give it a little gas it starts going but for a quick second it seems like that the transmission dis-engages and then re-engages and the tachometer jumps from 1K to 3K. If I wait about 10 sec after I start the car and then put in gear everything is OK.

The other day something strange happened, 3 min after cold start, I wanted to merge onto the highway so I mashed the gas all the way to the floor but it stayed in the same gear and did not kick down, now this has only happened once.

I did take it to the dealer and they gave me the “Could not replicate the issue” answer. I looked at the Highlander forums but did not find anything.

Any idea what might be the issue? I looked at the trans fluid, it seems OK and there is no evidence that the previous owner has done any towing with the car and it has always been serviced at the dealer.



Sajeev answers:

Automatic transmissions (and transaxles) are smart cookies, what with all their fancy electronic controls controlling a byzantine system of fluid pipes, valves, clutches, fans etc. There’s a reason why internal transmission problems are normally handled by repair techs with a particular set of skills. Like this guy:

If there are no check engine lights, the electronics are probably spot on. That leaves the fluid or that byzantine system to blame. Since your ride is under warranty, I’d leave it with them overnight to see if they can recreate the problem first thing in the morning. Pick an especially cold week for this, and insist it’s kept outside (if they don’t already). Odds are the dealer is right, it’s operating within specifications. It’s just that the fluid is maple syrup-ish when cold.

There’s a good chance that switching to fresh fluid (maybe even synthetic, if this is true) will help the byzantine system work better when cold, mostly because newer fluid could be more viscous when cold. That is, cold fluid can be thicker, harder to move in the system and resulting in everything moving much sloooooower. Be respectful of that and the transmission will respect your time and money.

If you want to keep the Highlander past the warranty, consider a preemptive fluid change at 75,000-ish miles.

[Lead image: Shutterstock user Pit Stock]

Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.

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3 of 20 comments
  • George B George B on Dec 02, 2014

    There is a phenomenon with automatic transmissions called "morning sickness" where clutches engage slowly when the transmission is cold, but operate normally once the transmission warms up. Generally it's a bad sign of expensive repairs in the future. Unexpected in such a relatively new vehicle. I'd leave the car parked at the dealer overnight and make an appointment with the service department to demonstrate the problem from a cold start with you present. I have a beater with a bad transmission that has survived more than a year with severe morning sickness. For cars worth less than the cost of transmission repairs, transmission failure can be delayed by being very careful how you drive when the transmission is cold. Wait for clutches to engage for reverse or drive before accelerating slowly. I have to shift the automatic manually for about the 1st mile. Shifts fine once it warms up.

    • Danio3834 Danio3834 on Dec 02, 2014

      Sometimes a shot of brake fluid down the dipstick will at least temporarily help a morning sick trans. It helps swell any leaking seals and can make a difference if that's the problem.

  • Danio3834 Danio3834 on Dec 02, 2014

    Sounds like a hydraulic pressure problem not applying the clutches correctly. It could be a solenoid or mechatronic/valve body issue not directing the pressure correctly, or could be a leak in a clutch circuit. Either way, the dealer needs to have the vehicle under the conditions which it occurs so they can duplicate it and see what is and isn't going on inside the transmission. Keeping on them about the issue even if it can't be duplicated at the time helps your chances of getting it covered outside the warranty if it outright fails later.

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