Wondering if anyone has heard this..

Ive been searching online and haven't found something that I feel is the same as my problem with video examples, so I wanted to upload mine and see what someone thinks. My truck is a 2002 Tacoma with the 3.4L in it. It has around 125,000 on it and was a 1 owner before I got it. I know the previous owner did the timing belt/water pump service at least once (records show the timing belt was done 2 times in a 20,000 time frame) but when I bought it it had this issue. When I first start in and it's cold there is no noise, but as soon as it warms up this noise pops up.

When idling in park, it does not make the noise. Once you put it in drive, the thumping begins. I can feel it in the shifter and the steering wheel etc. It is a very low pitch and seems internal, not anything like an engine knock per se. The sound does go with rpms, and is mainly heard at low rpm. We have had it looked at before and some said it could be the main bearing, but at the same time we never got a definite answer. The truck runs great, I am more curious to just see if there is a known issue I am unaware of or if this is something that doesn't happen often. Thanks for your input.

http://youtu.be/x_PwrXVXVTk

http://youtu.be/Row0G-M8sj0

If you listen closely you can here the thump

 

Sounds like a normal 3.4 to me, but I am on my laptop which has some royally shitty speakers.

 

That doesn't sound normal. Maybe you could sea foam it and see if it improves

 

yeah that sounds pretty bad. How long have you had the truck/like that?

If there is an unusual amount of vibration, and a noise like that, then something is definitely having movement outside of its intended boundaries.

Things you said:
When it warms up = when oil gets thin
When you put it in park = when a load is put on the motor

 

I had the same sound pop up when I changed my belts. Tightened them too tight. Then I loosened them and the sound went away for the most part. I'm thinking it's the water pump making the noise.

 

Maybe this will help. Post #8 shows a diagram of the area I think the noise comes from... the expensive part. http://www.tacomaworld.com/forum/1st-gen-tacomas/313705-really-bad-sound-water-pump-area.html Although he didn't say the noise happened in drive only, he did say that it was a "racket" and not a "squeal".
I caused the same issue after a belt change and I searched here for a fix, only to find other people scratching their heads. I did alleviate the knocking noise by loosening the belts, reducing it down to an audible "thump", now that's almost gone too I also felt the knock in the gear selector, but it's gone now. This has been over the course of a year btw. I feel it'll come back to haunt me some day though. The way I see it, the knocking sound is resonating throughout the engine from the mounting bracket of the fan clutch assembly.
If somebody knows more about what's going on here, please let us know. I'm working with no Tacoma knowledge, I owned a Sonoma for 15 years and worked on pretty much nothing else. If I sound like a fool, so be it, I want to know what our problem is so it can be fixed.