2021 OR transmission shudder/surging at speed

Great info!

Do you have the TSB number? It might give @BlueTaco4x4 a place to start?

 

If the engine speed changes, the vehicle speed also has to change or something has to give. Of course there will be some transient deflection in the drive shafts, gears, tires, etc. Not sure if that would be enough to smooth out vehicle speed or not with such small rpm changes.

If it does not do this with ECT engaged, that will at least give you a path forward for remedy. Slowly increase the shift schedules to run higher rpm until it no longer shows the problem. You'll get a bonus in my opinion, the truck responds much better when you increase the default low load rpms from the stock values. You don't need to increase them as high as the ECT values to see improvement.

 

This is the TSB that it had fallen under:
https://static.nhtsa.gov/odi/tsbs/2017/MC-10146516-9999.pdf

T-SB-0312-17

It says up to 60k miles, but I think they had extended it, because I just got rid of that thing with 140k on it, and the replacement happened in the last 3 years.

 

Agreed, esp with the TC Lock. But like you said, there's a lot of items between the engine to the wheels. I'm considering all that being damped out with the vibes that are seen. Also, I think the TC clutch might have a cush drive feature like an MT friction plate?


We did try an edited tune with modded AT maps. It was a bit better initially, but the issue was still there. After settling, the tune was holding gears extremely long. We met up again to get him back to Stock for the dealer visits.

I was thinking about having him run a fully unlocked tune, but with the vibes felt and the risk of cooking the ATF, it was just limited to a test.

 

Awesome! Thank you.

They will usually address issues out of warranty if they have been noted while in warranty.

 

I am not sure if there is a cush drive feature or not.

I think running a fully unlocked tune would be beneficial to determine if the problem is in the TC lock up. You can always monitor transmission fluid temps and stop when you start approaching 220F. The stock tune can easily hit 220F on transient occasions so this doesn't seem too unreasonable a cutoff for a tune that is not intended to be run long term.

 

That will have to be the next step. So basically drop 256 in all of the TCL S2 and S3 maps for 4th, 5th, and 6th gear?

I'm also curious about your ECT suggestion.

 

Easily is an understatement

 

That is my understanding, which came from 04B04. To be honest I have not messed with TC settings on my 04A61. It seems a reasonable assumption the 21's would use the same maps, but maybe not.

 

December 15, 2020 MANUFACTURER COMMUNICATION NUMBER: T-SB-0124-20
Components: POWER TRAIN
NHTSA ID Number: 10186200

Manufacturer Communication Number: T-SB-0124-20

Summary

TSB: Some 2016 ? 2021 model year Tacoma vehicles equipped with an automatic transmission may exhibit a vibration under deceleration (coasting or braking) between 30 ? 10 mph. This vibration is felt in the seat, floorboard, and/or steering wheel. Follow the Repair Procedure in this bulletin to address this condition.

6 Affected Products
1 Associated Document

very interesting, kinda what i'm feeling.

 

It looks to be similar. I'm trying to avoid unlocking 04B04 in the hope that the TSB happens soon. I did have to unlock 04A61 though.

That TSB replaces a damper in the steering wheel and measures pinion angle and possibly replaces your rear leafs. To me, that would suggest a speed variable vibration. To me, the vibes frequency doesn't change with speed.

Of course, it is a course of action to try?

 

Running good when cold but not when warmed up or steady, annoying vibes at a steady speed?

 

Any chance you were logging misses during this run, or any run? My truck has always had a bad low RPM/Light load vibe that 93 addresses.

 

Drives way better to work in the morning when it's cool outside. Driving home sucks.

 

Only issue with my 21 OR (currently 1200 miles) was a slight engine stumble under moderate acceleration, premium gas was
the cure but now i'm paying for prem fuel just so the truck will run the was it should on 87.

 

I usually alternate between 87 and 93. 89 works on my truck as well knocking down vibes as 93, but Costco doesn't sell 89 and that's where I usually fill up.

 

Great suggestion.

I did not in the vF logs, but @BlueTaco4x4 did in OBD Fusion. There were some at the beginning of both of his logs. And there were a couple later, but nothing consistent with the issue.

These are the only misfires recorded further down in the log:

 

That's a low misfire count. Thanks.

 

Unfortunately!

Thanks for suggesting it though.

 

Sorry, but that was meant to be one or the other. When warmed up is it general shittiness? Or, do you have this rumble strip vibration issue going on also?