Harsh downshift when cold

In the morning I notice 2nd-->1st gear downshift is a little harsh/abrupt when coming to a stop.
I know its not axle wrap/etc, because as soon as it warms up..downshift is fine.
I've had the TSB, and fluid checked. The faster I come to a stop, the more noticeable it is..
I could weed through the TSB thread..but asked here first. THoughts??

 

Let the tranny warm up.

 

https://www.tacomaworld.com/threads/2016-tacoma-downshifting.474203/

A thread with the same issue was started this morning. I have the same issue and I follow like 7 other threads with people experiencing the same issue, hoping for a solution.

 

Yes, pretty sure they all do it to some degree. Right? no. Acceptable? No. Normal characteristic of the truck? You bet

 

@mesojdm did you ever get this solved?

 

Old thread, common issue, but still no definitive answer on what it is or how to fix.

Someone took their truck in and the dealership said it was fuel moving in the gas tank. I don’t think that’s the case because it happens to me at different fuel tank levels.

I personally think it’s related to cold transmission fluid and the way the TCM behaves

 

Low tranny fluid....as it warms up, it expands and the "low" issue is not as noticeable...... It's right on the edge of being too low and "acceptable"....

Add 1 1/2 qts and You'll be fine...

EDIT.... I did not mean just add 1 1/2 quarts...!! I meant ... have it checked properly as you are likely low on fluid..!!

 

Subbed .
Interested to find out what is going to fix this issue
What happens when you load the truck bed with 500 pounds ?
Do you still get the harsh downshift ?

 

I’ve noticed it twice and it’s been very cold here.

 

Same problem. Been to the dealer several times and they can’t duplicate it.

 

Happened on my 2nd Gen, now on my third. Which leads me to believe it's axle wrap because the trannys are different, but I'm open to other opinions. Once warmed up on both Gens I've had, it goes away.

 

@gearcruncher

Lock-up is prohibited under these conditions...


Does flex lock-up have the same prohibitions?
Regardless, it is not active in 1st.
Could this be a potential clue?

 

Mine doesn’t downshift harshly, but it does slip from 5-6 I believe. I have the newest tsb. I just chalked it upto turd gen problems

 

Well, I have a 2012 and it has always been hard to downshift into 1st when it's cold. Drive 15 minutes and it's not a problem. It is what it is.

 

I was hoping gearcruncher would.

As I understand it...

Traditional lock-up is achieved through electronic control via solenoids SLU(on/off) and SL(pulse width modulation).

Flex lock-up(a.k.a. half-lock) is achieved through electronic control via the torque converter clutch solenoid SL(pulse width modulation).
Supposedly, makes the shifting experience more pleasant and increases fuel economy.

My uneducated theory is, if flex lock is not prohibited by the same conditions as full lock, it is not disengaging the torque converter clutch from the 2-1 shift via solenoid SL.
As prohibition conditions subside, solenoid SLU kicks in and/or it goes into a different lock-up strategy.

Putting it in S3 supposedly cancels flex lock; can't remember where I saw it though. Coincidentally, I've never experienced the harsh downshift. I've pretty much avoided D and have used S-mode from the get-go; and now, S-mode with ShiftSense. Maybe those experiencing it can try S3 and see if it makes a difference.

@OVTune would probably be the best qualified to comment on the lock-up strategies.



Sorry for all the edits...

 

Another thing I would try is, letting it idle a bit in neutral; on a seperate morning.
Some will say it is no different than park; but revs change in neutral. My thought is without the load of park, fluid is circulating and pressurizing 'things'.
I've tried locating the fluid flow diagrams with no luck, so it just a WAG.
I'm not saying it's a fix, but it might be a clue.

 

Mine hasn't done it in a while. Not sure what it is, but I do have the OV ECU tune now. I'm still leaning towards axle wrap if it's a sudden stop.

 

I forgot, I did have a TSB done as well. I'm just guessing with axle wrap

 

had 2004 GEN1 auto had it too till it warmed up about 5 minutes of driving,clocked 260k miles on the truck without any transmission malfunctions, it is what it is #2, and just drive it.

 

I have the same issue only when my truck is cold. Doubt it’s axle wrap. I’m thinking something to do with the shift points and the ecm. Last time I heard toyota was working on another update to resolve that issue.