driveline vibration?

I have a 2005 PreRunner, 4 door long bed, with 275k miles on it. Its completely stock. I have noticed a vibration when driving over the last few months, that keeps getting worse. It starts around 45mph, and gets worse from there. I thought it may be bad tires, but that hasn't been the fix. I'm not sure what to check now. The bed has a bad mount so it has a little play from the front passenger side bolt, and is only getting worse from this new issue. Has any one else had this happen, and if so, what do I need to look at and possibly repair/replace?
It has been my daily driver for almost 18 years now, and I've never took it off road or abused it that way.
Thanks for any advice.

 

A stiff U-Joint or failing carrier bearing would be my first suspects, sometimes a visual inspection will reveal which one is bad otherwise I'd pull the driveshaft (make sure you chock the wheels first), and check all the U-Joints for play or roughness/binding.

 

yep, what @Dm93 is saying...check the drive line, especially with that amount of mileage. Have you ever greased the U joints? Just honestly curious...

 

I had the u joints replaced by Toyota a couple years ago

 

Drive it 4th gear. If they go away, it could be the torque converter OD lockup failing. I’m expecting something based on your being around 45mph when it happens.

 

ok not the U joints, carrier bearing replaced also?

 

Is the vibration rear end or front? Everything posted is addressing rear end. If your first thought was wheels/tires, and without knowing front or rear, could be something as simple as control arm bushings or balls joints etc. Again, with miles, those all wear out. I have noticed tacos a very noticeably symptomatic compared to other makes / models.

Edit: Better question, can you feel it on the pedals?

 

What would feeling it in the pedals mean? I too have a vibe that I can feel through them

 

Just something for me to gauge a guess better without actually being in the vehicle. If you had floor board vibrations on the trans tunnel or nothing in the cab but rear end, then I would start to guess at drive line. If it's in the cab and you can feel it in the pedals, I'm leaning towards front end, and given the miles, I think it would be easy enough and worthwhile just to roll into an alignment shop for a visual inspection etc because this doesn't sound super driveline to me and sounds more front end issues. Tie rods even. Getting to a point where it's a hard guess online but would be easy to rule out visually and physically being there. If that comes up clean then I would move on to more oddball problems.