Chasing Vibes. Driveline or Torque Converter?

Developed a new vibration last week, probably better described as a relatively harsh shaking, throughout the whole truck on light acceleration between 15-20 MPH under just the right amount of load. My first inclination was suspension/ tire balancing issue, but the more I got to researching I started thinking about failing driveshaft components even though nothing was audibly or visibly worn out. So, I pulled down my rear DS since there weren't any obvious visible or mechanical defects with u joints or carrier bearing to articulate each piece. Front and rear U joints were vaguely resistant in one direction compared to the other but no clear binding. CB and center u joint felt like butter, although I'm no expert on what condition to expect from a worn out CB. Regardless, I decided to go ahead and take the truck for a spin on 4HI without the rear DS and I couldn't replicate the vibration whatsoever. Bingo, right? Ordered a Tom Woods single piece and I'm currently waiting on it to show up.

BUT!! Researching further, I'm now learning more about this apparent torque converter shudder, and reading how guys describe their symptoms sounds so eerily similar to what I am experiencing that it's got me scratching my head. I'm just over 90k and have yet to drop my truck off to let Toyota give er the ole' flush-n-fill-oops-wrong-drain treatment. It seems obvious to me that if the vibration didn't reoccur with rear DS removed then I dodged that bullet, yet I'm but a wee lad who is constantly schooled by you knowledgeable folks. FYI: I did drive in 4HI prior to removing DS and DID get the vibration.

Share with me your judgment, oh wise ones.

UPDATE 12/21/21:

Got the Tom Woods one piece driveshaft installed. No change to vibration/shudder.

Toyota tranny fluid exchange. No change to vibration/shudder.

Getting tires rotated and balanced now although I’m pretty confident that’s not my issue.

 

Is there a lot of up and down movement of the center bearing? Probably a good idea to do the driveshaft

 

I mean it moves but I wouldn't describe it as a lot. I read that 1/4" in any direction is tolerable and I seem to be within that window, maybe just outside.

 

Ok. At 90k the shocks are good? I would have tried new u joints but that one piece driveshaft might be sweet. Oh, hey killer looking truck!

 

Yup. Running billys. I think suspension/ tire balancing can be reasonably ruled out though right? Axle wrap could still be in play but allegedly the double cardon joints on the Tom Woods one piece should be able to handle those harsher angles.

 

Tire balancing: lead weights or ( the name escapes me) bag of beads? These things

 

I wrote this in another thread...

"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."

You could of tried in S3, a brake tap test, monitored flex lockup...

IMO, 90K is overdue for fluid service.

 

Yes I did read your exact post hence my new reservations. Again, didn't suspect TC until after I had ordered the one piece. Regardless, wouldn't TC shudder have remained obvious even though I was only driving on front DS? Why would the symptoms have gone away?

I'm going to take it to get fluid service after driveshaft install

 

It's possible, without the driveshaft connected, the same conditions are not present to highlight the shudder.
Also, 4wd might do something to converter lockup.

 

I suppose. However, I did check to make sure 4HI wasn't an outlier before I drove w/o rear driveshaft and I was able to replicate the problem.

 

If I may suggest - spend the $99 on the Apple/Android App Store and download the NVH Vibration Diagnosis app. If you google it first, you will find multiple youtube videos. It showed me how my vibration issue in my 17 DCLB was in the driveline, not the engine or tires/wheels.