Low RPM Shuddering

Need help diagnosing a shudder/violent vibration. It only occurs when driving between 35-45 MPH but most commonly at the 40 MPH mark and usually the truck is in 5th gear when it occurs. If I downshift the truck to 4th gear the vibration/shudder disappears immediately but I believe this is due to RPM's being higher.

2012 Tacoma 4WD 196,000 Miles:
-Bilstein 5100 (top setting, stock springs)
-rear add a leaf (no idea branding, purchased truck second hand)
-angled shims under leaf springs
-new front CV axles both sides
-needle bearing replaced
-265/70R17 tires on Stock Wheels

If anyone has any idea what to do to fix this I would greatly appreciate. Feel like I have banged my head over and over looking for answers and solutions with no luck.

 

Welcome to TW, research torque converter shudder, most likely culprit for most of us.

 

As others have previously written on a torque converter thread (Is this torque converter shudder? | Tacoma World) it definitely feels like a rumble strip under the light acceleration. Appreciate the insight

 

I had similar issues. 35-40mph with shuddering. I went to replace my VVT and ended up putting the old one back in, but just removing one and putting it back in actually helped. I still get the shudder at 40mph, but ONLY at 40mph. My finances aren't great right now, so I haven't replaced the VVTs, but that is on my next to do list.
Check this thread out.
https://www.tacomaworld.com/threads/2nd-generation-transmission-shudder.808889/

 

This thread seems to describe the exact issue - what it seems like is I need to differentiate between engine shudder and torque converter shudder to identify which one is the problem

 

You are exactly right. Owners may be chasing an engine issue when it is really a trans problem. The torque converter clutch locks around 45mph. So if the shudder occurs then try disconnecting the electrical connector on the side of the trans for the TCC and test drive. This will keep the TCC from locking up and the shudder will disappear if its the problem. Not saying the torque converter is bad, yet. Worn out fluid is the cause of a lot of shudder issues. With 196K miles on your vehicle you should have changed the trans fluid 3X by now. If not, you would not be wasting time and money by doing this. Keep in mind that if you drain and refill you will be replacing only about 3 qts in a 10 qt transmission. So you may have to do this a few times to get all new fresh fluid in the trans. Or take it to a shop and have a "flush" and fill performed.

 

Drive it in “4” if it doesn’t shutter it’s the converter. Do a filter change and add some lubeguard anti-shutter. It will work for a while but will come back.