2005 Tundra transmission slipping...or engine misfiring?

2005 tundra with 200k…either slipping transmission or engine misfiring…for last 3 years. 6 mechanic shops plus dealer and no one has a clue or wants to touch(??)
Spent $3000 trying to get an answer or a fix.
The truck runs great at low end speed or higher speed/acceleration.
Between 30 and 60 if I try to accelerate too fast…it acts like it is misfiring or transmission slipping?
Have been told it is likely torque converter but I assume that means a new transmission…replaced plugs 3 times so assuming it isn’t engine.
Again it runs great at higher speeds.
Anyone?

No codes?

Usually when there’s a misfire, the Check Engine light will come on with a P03XX code.

Maybe what you’re feeling is torque converter clutch shudder.

You might consider trying this product.

http://www.lubegard.com/~/C-250/Dr.+Tranny+Instant+Shudder+Fixx

Tester

You’ve been dealing with this for 3 years?!

This shouldn’t be that difficult to figure out. If the transmission is slipping, the engine speed will increase without an increase in vehicle speed. Is this what’s happening? Has the transmission fluid been changed as per the maintenance schedule?

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Concur w/posts above, first step is the diagnostic codes. Nex ask you shop to temporarily install a tachometer in the cab so you can monitor the engine rpm as you drive. When this problem occurs, is the tachometer increasing rapidly while the speedometer isn’t? If so that’s something related to the transmission or torque converter. If not, most likely it is an engine related problem. If I had to guess I’d say it was the former, as it is pretty apparent to a mechanic when a misfire is occurring.

Not to sound like a spoiler here . . .

I’ve fixed MANY problems which did not generate trouble codes

And some of these problems profoundly affected driveability

So if somebody doesn’t know how to proceed if there is no fault code . . . their diagnostic skills may be woefully inadequate. Might need more training, or they may have to start reevaluating how they perform their job

Thank you…I couldn’t agree more.
Do you have any thoughts on what might be causing this?
I’m hearing several say transmission/torque converter

Issues with the torque converter had also crossed my mind