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.

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.



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

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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

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Hello, did you ever get to the bottom if this issue? I have the exact ghost haunting mine. 2005 Tundra V8, at 2500 RPM cruising between 45 and 60 it will just feel like the overdrive is going on and off. No dash lights, no codes, checked live data… I have already checked the overdrive wire inside the column that commonly fails, and the main 15 pin harness on the trans that commonly corrodes. My harness was destroyed and I had to replace both sides. After the 10 hour job I am horrified to find I still have the original issue described…

Thank you!!!

Well since others don’t like anyone piggybacking off an old thread it is best to start your own Topic on this forum…

That being said you may have a TCC kicking in/out, might try slightly applying the brakes just enough to turn on your brake lights and see if it stops doing this…

This just a possibility and you would probably be better off having a transmission shop or dealer diagnose it for you…

2003 and newer Toyota and Lexus vehicles equipped with the A750, A760, A761, A960 and AB60 series automatic transmissions. (looks like you have the A750E) Common complaints with these transmissions are shuttle shifts, bind-up or flare on the 2-3 shift, slips with throttle in 3rd and/or 4th gear, solenoid and TCC performance codes as well as rough kickdown at highway speeds due to slow TCC release.

The first area of concern leading to the TCC complaints is a worn-out TCC relay valve bore. When the TCC relay valve bore has excessive wear, the computer can no longer control the apply slippage and the release rate of the lock-up as it is supposed to. Additionally, the TCC control valve and bushing is prone to wear causing lock-up control complaints as well.

The other area of concern is a worn-out solenoid modulator valve bore. The purpose of solenoid modulator valve is to limit the pressure going to solenoids, just like an AFL valve or solenoid pressure regulator valve does on other units. The modulating valve and spring are calibrated to prevent solenoid feed pressure from exceeding a predetermined PSI, no matter what main line pressure is. This is necessary to prevent more fluid from being fed to the solenoids than they can effectively regulate and to limit what max line pressure output is. If the pressure feeding the solenoids is too high or too low, output will also be too high or too low. Consequently, shift quality complaints, solenoid performance and gear ratio codes can occur along with low or high main line pressure.

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Engine misfires can seem like a torque converter problem, so don’t entirely rule that idea out. When problem seems to be at its worse, stop the truck & get out, but let engine idle. Hold a $1 bill near the tail pipe. It should always move away from the tail pipe, possibly in bursts, but always moving away. Does the $1 bill ever move towards the tailpipe? If so, that’s a very clear indication of a misfire.

Thanks George!

I was about to remove the trans valve body, bore the modulator and install a shift kit when I decided to look at live data one more time.

I was not getting any dash lights/stored codes, but live data picked up a #8 misfire. I pulled the coil and found a 2.5" crack in the plastic body. I replaced all 8 coil packs and she’s ready for another 300k!

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Thank you!

This case turned out to be an intermittent misfire that was not sending a standard code and I had to find it in live data.

I did a ton of reading about this trans and you are correct about the TCC concerns and I will likely install either a Sonnax or TransGo kit in the near future. Do you have any preference or advice about either or a different brand/option?

I appreciate your help! Both companies claim to be the best obviously, the Sonnax seems to be a bit more of a complete upgrade/refresh, but the TransGo seems to attack the very most common issues with a bit more of an involved installation procedure.

Thanks again!

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Transgo all the way… TransGo finds the issues causing the failures and corrects them in the valve body… Gil Younger founder of TransGo is one of if not the 1st “Shift kit” builders… In 1959, Gil opened TransCo, which became TransGo , a valve body repair kit company whose primary goal was to diagnose, correct, prevent and reduce transmission complaints with time-saving and easy fixes… I have been using them on every build for over 30 years (if available), and was informed about them from a retired Master Transmission builder that one of the top transmission builders back then… Meaning if a transmission shop/builder was having a problem with a transmission they could/would call him and he could explain how to repair it over the phone… He was that good… I learned a lot from him…

TransGo is also the only Shift Kit for performance shifts (not like the one you would use) that I will use on a A904/998/999 or A727 transmission… My A999 with the TF3 full manual feels like a Mule is kicking you in the back when you hit 2nd gear and the car is being rear ended by a big truck when hitting 3rd gear, and I don’t have the PR turned all the way up, it is set for street racing, I mean driving… They do make versions for Mild shifting also…

But to answer your question, TransGo only… Not saying the other is bad, I just know TransGo is that good… lol

EDIT: Advice, read the instructions multiple time until you 100% understand what to do…
Take your time and carefully remove the spool valves and springs etc and lay them out in order being careful not to turn a valve 180 degrees , they might go back in a few different ways and fit, but only one way will work… If you don’t mess with VB’s much then you can take tons of pictures… Good idea any just incase you bump the table and a valve or two roll…

AND most importantly clean everything, a human hair can stop a valve from moving and burn up a transmission…

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