Driveline vibration of axle/transmission shaking

Hi everyone, I am new here and this is my first post. I am used to many facebook groups, and I did many researches there before. But today I need your help with an issue that I cannot solve.

here is the problem:
A few days ago I drove about 500 kms on 4 hi on a gravel road which was snowy and icy and when I came back to the pavement I switched back to 2wd and noticed an issue. When I was speeding from a complete stop, at a low speed and a low RPM ( 1000-1500 ), the truck shook very intensively and the issue occured every time the truck shifted to the next gear and rpm dropped to 1000-1500, always when speeding... today the temperature here has reached 10 C so everything melted under the truck and on the wheels, and the issue is the same! I feel like it comes from the tranny, the drive shaft or the rear diff. I carefully washed the wheels, and everything under the truck to eliminate all the snow and ice that could be anywhere and I took off the last rear section of the driveshaft to apply grease to the slip yoke and inspect the U joints and the center bearing ,that seem in very good shape. Do you have any idea? Truck has 77k kms. It praticaly feels like missfires that disappear at 1500 rpm and above and only occurs when pressing the gas pedal just enough to provide a mechanical leading but not enough to downshift. It is not quite a feeling of an unbalanced wheel either, since the cycle of the vibration is faster than the spinning wheels speed

 

Fried atf and/or glazed the torque converter clutch.
Check, smell fluid?
Try driving in S3; does it go away?

 

I am wondering how could this happen with its oem atf cooler... considering it only has 50k miles and towed only a few times!

I will add this fact: on my 500 kms ride there were 250 km of the road that has not been recently plowed and I did not use neither S4 mode nor etc button... maybe riding this way in fresh snow for a while on 4hi, low rpm did not allowed the atf to cool enough ?

 

300 miles in 4 hi on slippery terrain and the torque converter out of lock up...I can see it happening.

 

I don’t know about lock up fonction, could you tell me more about that? Thank you

 

Full lockup occurs when the engine is locked at a 1:1 ratio with the transmission input via torque converter clutch engagement. It usually occurs when cruising, at around 40 mph.
There's also a partial duty, called flex lockup that occurs at various speeds/gear changes during acceleration and deceleration.
Basically, anytime the torque converter is not in full lockup, it's generating heat. How much heat depends on how much 'slip' between the turbines. Things like towing or slip-sliding down an icy road for hours on end with a 'more pedal' mentality can generate a lot of heat.

 

Very clear explainations, thanks! So I guess that the torque converter is automaticaly locked in S mode and this way cannot use its flex mode ?

 

No...full lockup can occur in D or S.

The reason I suggested S3 is it should eliminate flex lockup.

 

I see, so according to you, if I had use the S4 mode during all my last ride (as toyota recommands for towing), would it has helped to eliminated flex lockup and keeps the trans less hot in temperature ?
Sorry , I am asking many questions but it is hard to believe that truck is not meant for this purpose and I try to know what could I do different to avoid this issue! S mode ? Etc button?

 

It does not go away in S3, shudder still there but maybe, less often. Could this even be the torque converter? I will bring it to the dealer to have the atf checked

 

I suggest a missfire test .

You feel the shuddering at 1500 rpm in every gear ?

Warm up the truck
Put the transmission in drive with your foot hard on the brake pedal and bring the engine revolutions up to 1500 in your driveway .
Do you feel the engine stumble when the rpms hit 1500 ?
This is a missfire test .

Allow your transmission to cool after the test by running the engine with the transmission in park

Here are more vibration tests
https://www.tacomaworld.com/threads/vibration-diagnostics-for-all-tacomas-write-up.520607/

 

S3 is a bad idea because the TC will never lock.

Driving in 4HI is no different than 2HI as far as the tranny is concerned. It doesn’t heat up faster.

 

I do not feel it in every gear. It occurs when the rpm is downed to 1000 or under after an upshift and when I gently keep the gaz pedal pressed ( not enough to downshift but enough to maintain a weak acceleration)
I will do do the missfire test tomorrow and come back

 

That was the intention, as It was a test to see if the tcc might be affected.

 

Gotcha. I misread that.

 

I absolutely dont feel the engine shuderring when executing the missfire test

 

From what I have read on here, many 2016 trucks with the AT were shipped low on ATF from the factory.

You could try checking the ATF level yourself. I bet its low. There are several writeups on here, though I dont specifically know the sequence for 3rd gens.

Probably wouldn't hurt to do a drain and fill while you were at it.

 

Op's truck sounds very similar to a buddies 2019 trd where the engine lugs at 1000-1200 rpm and shakes the truck. Seems its real noticeable around 35 mph. He can't recall doing it with the stock tires and height...never drove it long enough before giving it a lift and 33'' tires.

 

Thank you for performing the shudder test . An engine missfire is now eliminated .
Do you know if the dealer updated your transmission computer ( ECU ) with a technical service bulletin ?
The dealer would have placed a new sticker under the hood of the truck
Are you positive they checked the transmission fluid level ?
Becuase the transmission is completely computer controlled , are there any trouble codes ? I hope you have a scan guage / ultra guage ?

 

The question is : if i’m low and I drove so during 4 years and then I check the level myself and add 1 qt for example, would I hide a fried fluid issue that itself caused my torque comverter to toast ? Who knows and how to know ?