Driveshaft Vibration

Hey guys, I've been fighting a driveshaft vibration for quite some time now. Been reading a lot on forums and cannot find a solution. I would really appreciate some help.

Truck:
01 Tacoma 5-speed RWD (2.4l engine) (Single piece driveshaft) (Completely stock truck - 230k miles)

Problem:
Shuddering during acceleration. It has become so violent to the point I can no longer drive it. It does not happen in first gear (may be irrelevant), usually in 2 gear and higher. I put truck on jack stands and had someone drive it. There is a clear shuddering sound heard through drive line.

What I've done so far:

• I replaced both ujoints. This changed the characteristics of the shuddering (i.e. what RPM it begins, speed, etc.), but ultimately it is shuddering just the same and is only getting worse with each test drive.
• I checked the engine mounts and they look solid. Tried shaking engine, no movement whatsoever. It is on tight.
  
• Check Transmission mount. Also appears solid.
• Removed driveshaft and checked diff flange bearing. No movement in or out. Rotates slightly, but sounds like I'm moving gears in the diff a little, feels normal.

I read around that pinion angle may cause this issue, mainly on lifted trucks but also can happen from weak leaf springs. I did a lot of measurements so I will do my best to explain.

Transmission: 87.8 (pointing to ground - from 90 deg)
Driveshaft: 5.3-5.7
Rear Diff: 88.1-88.3 (pointing up - from 90 deg)

This would make the difference between Transmission and Rear diff .3 - .5 degrees. The joint angle at the rear diff to driveshaft is 93.4 - 94 degrees. Does this look correct? I am a bit confused if the difference between the Trans and Rear diff needs to be as close to zero as possible, or if the rear joint angle needs to be as close to 90 degrees as possible.

 

One thing is always over looked is the bushing in the extension housing on the trans. The output shaft on the transmission is the rear support for the shaft as it exits the transmission... how much is too much for vibration... dont know.

If during the u-joint replace the caps were pressed on to far to the point of binding the cross this will induce a vibration due to the u-joint not being smooth opperating during it rotation/cycle.

assuming there is a flange on the trans output and a flange on the third member... mark where they are right now, remove the 4 bolts and rotate one or the other 90 degress, retighten and go for a drive, if still there, rotate another 90 degress... it doesnt cost anything but a little time.

 

This is written for 2nd gens but a lot of it applies to 1st gens.

https://www.tacomaworld.com/threads/drive-shaft-vibrations-solved-step-by-step.244535/

 

I have read through that thread earlier. It seems that they made sure that the angles canceled each other out and then adjusted center bearing to 'tune'. I have a single piece drive shaft. I measured again, and the difference is between .5-.8. This to be very good as it is less than 1 degree variance. Please correct me if I'm wrong, I really want to solve this issue without throwing parts at it.

As for the caps being pressed too far, I do not think that is the underlying issue. The vibrations started before the ujoints. The original ujoints did not feel like they were loose or bad, but I replaced them to make sure they were good.

In regards to the alignment between rear diff and trans output, I was originally not aware of this until after I had removed it. I would like to align this, but cannot think of any way except to try every variation given the 'teeth' on the trans side. I also do not think that this is the underlying issue causing these vibrations. The driveshaft was aligned before I took it off, and the violent vibrations started with it being aligned originally.

I took some videos that hopefully give you an idea of what is happening. I put the jack stands on the axle in attempt to replicate the height when sitting on ground. The center jack is only for backup (not holding anything).

Rear Diff:
https://www.youtube.com/watch?v=YX-yNm_iimA

Trans side:
https://www.youtube.com/watch?v=qZAMSi0HDeg

As a note, there is up and down (ground and sky) play on transmission side, feels like shaft (or bearing) inside has movement. I was told that this should not cause vibrations. I suspect this is true since there is no real vibration on transmission side (seen in video). Vibrations seem to originate from rear diff area.

Below are pics for visual reference.

 

If you haven't already, put a pry bar in the transmission mount and make it flex. You can't always tell if it is good by pushing on it with your hands. I had to replace the one on my 99 and I couldn't tell that it was separating until I used a pry bar. Look for it cracking where the rubber meets metal. Look for these same cracks on the engine mounts as well.