2021 OR transmission shudder/surging at speed

ECT mode yielded the same shudder/stumbling for me. The only thing that prevented it from happening was manual shifting mode. The ECU update has been done to my truck, but it is still in the shop getting the drivers seat frame replaced for the dreaded seat back play.

Will post the results of the ECU update after I've driven it.

 

Seems a strange issue as my buddies 2019 trd or appears to do the same as described. My 2020 is baby butt smooth, and quiet, no vibrations or shuddering at all...nothing. Imo, its the torque converter as a buddies won't shutter at all if put in neutral when braking to a stop.

 

I got the truck back with the TSB ECU flash. Low RPM between 35-55 MPH still produces a stumble/vibration/bounce/shudder, whatever you want to call it. While I was driving cross county it was very noticeable while going up hill.

It seems like this truck is bouncy all around, as it is long and narrow, so this could be contributing to the problem. Or it could be the torque converter. My truck has lifetime powertrain warranty so while this is annoying I am not that worried about it. I'm just going to give her a tune.

 

Found the bounciness really sensitive to tire pressure...couple psi high and its really noticeable. I don't think the shocks are dialed in well either...they could use a bit more rebound valving. As far as the torque converter issue...seems its more noticeable on some trucks than others.

 

Well my 2020 v6 is just the opposite, runs sooty rich at the tail pipe on shell premium with less performance and fuel economy. Its a different truck on 87 grade fuel.

 

Its not uncommon to have a converter clutch shudder on a new truck . The clutch design is similar to the clutch used with a manual transmission only the clutch is controlled by the computer in your truck rather than your foot . Everything mechanically has to be perfectly smooth and true inside the torque converter for this to happen . There are a lot of moving parts inside the converter .
I have seen many brand new converter clutches have issues with shuddering . A quick fix is lubeguard Platinum , but it doesnt always work depending on the severity of the shudder .
With the way the Tacoma operates during flex lock up , its like a guy riding your clutch in a manual transmission all day long .
Flex lock up in a nut shell partially applies the converter clutch . This means the clutch inside your converter gets to slip every single day you drive your truck in an effort to save you fuel . If I had my way , Use OV tune and eliminate the flex lock up completely . Use the converter lock up feature at freeway speeds only .
Guys always point out the converter because problems are most noticed when the converter is applied or partially applied
Not saying this is your problem without better diagnostics on a lab scope . Issues like this generally need to be connected to a lab scope that looks at parameters 32 times per millisecond . Its not something you will likely see on a generic scanner.
Call corporate and get the ball rolling

 

Same jerky issues 40-50mph @ <1500rpm. I now drive S5 all of the time unless on the highway. Seems to prevent 80% of my issues.

 

I will mess around with my PSI and see what happens.

This afternoon I got the KDMAX tune. It resolved many of the issues I didn't like about the truck. Bounciness is somewhat still there at low RPM. Overall it drives way better than the stock tune. I'm getting 18-22mph per trip depending on conditions (city driving, didn't get a chance to hop on the highway.

The tune I did was the LT 87 octane. I'll be switching to the 91 octane tune to see how it changes things. Hoping for a little more power out of the engine.

 

Happening to me too...

Have a 2020 SR5 that’s about 6 months old and it just started doing the shudder/hiccup/stumble type thing… first noticed it just prior to about 6k miles.

Most of this seems like the same info that's been shared, but I'll share anyway just in case:

It’s most noticeable at highway speeds when just trying to maintain a constant speed. It’s scenarios where the truck should just be smooth, but instead you feel a random back and forth kind of herky jerky motion. It’s sometimes subtle, could almost be confused for road vibration at times, but whereas road vibration is more of an up and down motion, this is a more forward and back motion. Other times (randomly) it’s suddenly way more noticeable and will really jerk back and forth. But mostly it’s just constantly a subtle random forward back kind of hiccup.

I’ve noticed it at various speeds… occasionally even while idling it’ll randomly hiccup and kind of do it… but it’s most common (or most noticeable at least) at highway speeds.

I tired to explain it as best I could at the dealership. They said they struggled to reproduce it, and then told me they’d fixed it by replacing the rear drum breaks, that the rear drums were misshapen and that it was a known issue. Of course, replacing the rear drums had nothing to do with it and it still does it just the same. On the receipt the tech listed something about ‘replacing the rear drum brakes lessened the shudder when braking,’ which wasn’t the issue so I’m not sure what that was about.

Now that I know it could be the torque converter, I'm curious to get it back into the dealership, share a lot of the info from this thread, and see what comes of it. Though, based on some of the other stories here, I'm not super optimistic.

 

Has anyone tried Lubegard Instant Shudder Fixx?? Either as a fix or to help diagnose? I haven't yet, but am intrigued from all the glowing reviews of it.

https://www.lubegard.com/products/isf/

 

Lubeguard is a fix used to assist in removing the glaze off the converter clutch dampner . Lubeguard should not be used on a brand new transmission .
In my opinion , I think you need a more in depth diagnosis of what is actually happening with the truck .
Dont get me wrong ... Lubeguard is great but shouldnt be needed with a brand new trans without some in depth diagnostics

 

Is it detrimental to a new transmission? Or just shouldn't have to be used? Just trying to understand more...

Totally agree on needing a more in depth diagnosis.

 

Lubeguard is not detrimental to a new transmission and you can add it anytime during the lifetime of the truck .
I actually use it on every transmission I rebuild . The stuff is that good , however , in my opinion , your transmission fluid is brand new . The reagents in your fluid have not broken down yet , therefore , I believe you need to look at other causes first before calling out the converter clutch.
I highly suggest playing this out with your dealership and Toyota corporate before throwing Lubeguard at the transmission .
You are welcome to add Lubeguard to your trans anytime but in this case , I doubt it will help .
99% of your issues are caused by the programming boys at the Toyota plant trying to hard to save you fuel .
The result : you get good gas mileage but suffer through the drivability issues when the truck upshifts into the next gear too early

 

You have described my issue perfectly. 2019 4x4 3.5. Mainly seems "stuck" in gear and won't shift down, almost like a lugging/engine-missing sensation. Sometimes when it finally downshifts I swear I hear valves clatter.

I haven't heard clattering valves for 30 years. WTF is going on with Toyota??? You're right...it almost feels like road bumps/vibes sometimes.

 

I always tell people to try some 93 if they are having a miss or weird vibe. It's a known issue on some trucks. Try some high octane, see what happens. Worse comes to worse, you are out $5 and can move on to the next suggestion.

My trucks has had a light throttle, low RPM miss/vibe/ping for 58k miles on 87, 93 fixes it.

 

Before i picked up my 2020 sr5 the dealer claimed the latest tsb was done that upgraded the transmission and engine performance, so i was the 1st one to put any miles on the truck doing the 160 mile ride home. This trucks transmission was crazy for about 1,500 miles till it got suddenly better every time i drove it. It did have some faint shuddering very early on, but that to now has disappeared. At slightly over 10k miles now you'd be hard pressed to complain about anything.
As far this shuddering, my buddies 2019 trd still does it really noticeable at low rpm, and he's got nearly 15k miles on the truck. He has the same latest tsb tune in his also. From what it appears not every bone stock tacoma with a v6 auto perform the same.

 

I wouldn't go out and buy another brand truck seems like they all have a shutter. Lockup converters, multiple gearing, electronic control long list of things a stick shift doesn't have!

 

Thanks, but that screenshot was only Engine RPMs on four different vF Logs.


Yes. Though, we were watching both SLU and Locked PIDs on OBD Fusion. There was not a moment of wavering or anything that would have made me think the ECU was commanding anything to the TC that was being felt. At times, I would feel a hint of a stutter starting and glanced at OBD Fusion to see it transition from Slip Lock to Full Lock. Here is a section of the OBD Fusion datalog:

The biggest issue there was that the log interval was 1/sec.


As noted, I did make the mistake of not logging on TechStream after I found the AT PIDs missing from the vF Logger.


The issue felt is constant shuddering at any steady speed, most evident and annoying, IMHO, on the highway holding speed.



One thought has come to mind, which might blow a hole in the whole logging effort. Are we monitoring the ECU commanded actions or the actual solenoids? Say that the ECU commands full lock, SLU and Lock, and if either of those solenoids are going in and out, is that data being reported or is it just the ECU command?


My other thought is that if the AT is truly locked steady during this situation, what other elements could cause an approximate and constant 10hz vibe over a wide speed range?

 

Commands...
It's supposed to use logic to determine if there's a problem. But, as we have come to find, Toyota's thresholds are rather high for some things.
It's great to go down the software side...
My fear would be ignoring the hardware side that software can potentially mask.

Camrys had/have similar complaints...
All the new programming and r/r won't fix a design flaw.
It relies on an interference fit between the input shaft and converter hub to be good enough to contain TCC apply pressure.
https://www.transmissiondigest.com/the-importance-of-a-positive-seal/

 

Well, shit. Then all the logging on the planet ain't gonna help. Hahaha!

Thanks for the info!


@BlueTaco4x4 . So, this may actually be the TC.