3rd gen torque converter shudder

Correct.

 

oh it had the issue before the lift as well... reported it to dealer within the first month of ownership.

 

The thing about bad slip control is it exacerbates other things; motor mounts, driveshaft vibes, etc. Then you get caught in a chicken vs egg troubleshooting paradox, as you have experienced with your uncertainty, regarding TC vs driveshaft.

 

I think a techstream scanner will help you pinpoint your issue . You can watch the converter being commanded on and off as well as partial apply . You can watch the converter turn off while you tap the brakes .
Some guys purchase a scan gauge to monitor the transmission temps . Its a worthwhile investment if you plan to keep the truck as the scan gauge shows you a lot of vital operating parameters
Some guys say filling the truck up with gas eliminates the vibes . This is all about driveshaft angles and nothing to do with converter shudders .

With only 5k on the truck , your next option is an aftermarket tune . Its sad the dealers cant come up with a better answer other than this is a normal characteristic of the Tacoma

 

You need to get some monitoring tools to isolate the issue.
There are phone based apps and cheap obd wifi adapters.
Does it happen if you drive with ECT on or in S4?
Check the driveline, u-joint, etc.

 

Which app and obd wifi adapter do you recommend?

 

I've been using OBD fusion with 2017 toyota PIDs pack($10 or so and year specific) and Veepeak wifi OBDII adapter for Android ($10-12 on Amazon).

 

Just did the test... the vibration stops when pressing the brake pedal

 

Lifting the foot of the accelerator unlocksTorque Converter

 

OK , but the brake tap test doesnt mean much at this point .
You are not actually hitting the brakes , your are just lightly tapping them . Tapping the brake pedal very lightly energizes the brake switch . When the brake switch is gently tapped , the brake switch commands the torque converter to unlock . I would be watching your tach . What rpm do you feel the vibration or shudder . Never mind vehicle speed , pay close attention to engine rpm .
If your issue is engine related , we can reproduce the shudder in your driveway without driving the truck . This will eliminate your complete driveline

 

Brake switch does not command TC, 0 % of accelerator unlocks TC.

 

1500 Rpm and below and yes, im only tapping it slightly im not actually breaking when i do it

 

Did Toyota change their programming in 2021 ?
A gentle tap of the brake switch use to command the torque converter to disconnect or unlock /switch off anticipating the truck to stop ?
You can hold your foot steady on the accelerator and tap the brake and watch the converter unlock on any scanner 1996 -2020 trucks
Been diagnosing this way since the electronic locking converter was introduced .
I agree that the converter will also unlock at zero throttle but not until the transmission downshifts back to first gear

 

Vibration does not stop when i take my foot off the gas pedal

 

I need to go write a procedure for you 3rd gen guys . I have a well written document for the 2nd gen trucks in my transmission write ups , but nothing for 3rd gen trucks. Although the procedure is identical for both generations , I think writing a procedure would assist in this situation .
In the transmission trade , we call it a " Brake Tap Test "
You hold your foot " STEADY " on the gas pedal . As you are slowly accelerating , you feel the shudder , you tap the brake pedal with your left foot as you hold your right foot constant to see if the shudder goes away . At the same time , you watch the engine rpm to determine the engine load at the time of shuddering .

 

Engine RPM goes up to 2000 when i lightly tap the brake pedal when i do this test

 

If you brought your truck to my shop , I would try a stall test next .
What's involved ?

Warm up the truck .
Put the transmission into forward gear , hold the brakes hard .
Accelerate the engine while you hold the brake pedal hard .
You are trying to reproduce that shuddering you feel at low speeds around 1500 rpm .
At this point in time , its not about the truck moving but more about if you feel stumbling at the same point in RPM where you feel the shuddering as you are driving the truck . Your truck is going to shake similar to what you feel when the truck shudders while you are driving it .
Allow the transmission to cool afterwards by idling in park .
I can do this test with ease but I have also been doing it for 35 years and know what to look for .
In cases such as yours , an oscilloscope helps but I dont expect you to go out and buy one .
Thats why you have warranty lol
Problem is , dealerships rely too heavily on scanning codes expecting the problem to be pointed out for them .
Sometimes , in cases such as yours , you have to dig a little deeper to find the problem .
Codes are just a guideline . 99 % of the time , there are no codes

 

I have no idea. I only based my statement on observed behavior of TC. Here is Techstream data. 6th speed. As soon the accelerator hit 0%, TC unlocks, locks up right way with the application of the throttle for given spees

 

Was able to have dealer hear me out and they said if they can verify TC shudder theyd replace the torque converter but my worries now are if that would solve the issue..... what even caused it in the first place

 

You wont see a " Brake Tap Test " under normal operating conditions .
Nobody rides the gas pedal and rides the brakes at the same time unless for diagnostic purposes .
Thats why you dont see this test in normal every day driving .
I like the way you debated the question though
There is nothing better than the parameters you provided

Leaky fuel injector , bad coil , bad spark plug plus hundreds more
All these issues come into play when diagnosing a shuddering problem
Yes , you feel the shuddering when the converter is locked up directly to the engine when your engine is under a massive load .
proper diagnostics are the key to fixing this .
The dealer wont give you the time of day to diagnose this properly