Shuddering, 1500-2000 RPM @ ~55mph, seems related to OD

The Truck:
2001 Double Cab V6 automatic.

The problem:
Truck has a shudder/slip between 1500-2000 RPM @ ~55mph. It started pretty intermittent but is now pretty persistent. It happens with light pressure on the pedal. Increasing or decreasing throttle makes it go away. The RPMs do not fluctuate so it seems more likely to be a power transfer issue than something like a miss fire. If the OD is turned off the problem cannot be replicated under any conditions.

Some notes:
I have taken it to my mechanic and his attitude is that I run with the OD off unless I am going at highway speeds, which is 70+ around here, and we monitor it too see what happens.

I have a TracRac with a Roof Top Tent and Thule Box as well as 265/75R16 General Grabber AT2s on the truck, it isn't towing but I am certainly carrying a bit of weight with me everywhere I go.

What I am hoping for:
Any ideas of what you think it could be.
Any ideas of how to trouble shoot to determine what the issue is.
Possible solutions to my problem.

Thanks for the help.

 

A shudder would indicate a problem with your torque converter lockup. Try this: when cruising at 55mph, lightly tap the brakes. This will unlock your converter. A few moments after letting off the brake, the converter will try to lock up again. See if the shudder happens when the converter is trying to lock.

If so, you'll need to replace your torque converter, which isn't too bad $ wise. Labor wise it's pretty expensive though. The trans has to be separated from the engine to replace it.

 

And the driveshaft u joints and center bearing are good?

 

Im betting you have bad spark plugs causing a misfire. I had a similar issues almost identical where itd only misfire under light throttle low rpm in od.

How many miles do you have on the truck?

 

I did a little testing with this on the highway right now and it seems to act as you suspected. If it is doing the shudder and I just barely get on the brake the RPMs jump about ~100 and the shudder goes away. If I then get off the brake the RPMs fall back and the shudder returns.

As for the other ideas:

I can't say for sure about the u-joints or center bearing but I will look into that.

As for the misfire idea wouldn't I expect to have check engine light to go along with that?

Truck has just shy of 230K miles.

 

Not necessarily true. I drove my truck around for roughly 500 miles with a very bad misfire that made the truck buck terribly and never got a check engine light. Not saying your truck is misfiring, just letting you know.

 

My truck felt like the rear end was bucking off the ground when I was in overdrive and the engine was under light acceleration at highway speeds. It turned out to be the plugs and wires. No check engine light. I guess being in OD it was lugging the engine enough to cause it to shudder. #2 plug wire was broke and about 1" of it was still attached to plug when I pulled the wire off.

 

I just got back from doing a bit more experimenting and have some results. In an effort to expand on yesterday's sample size I tried getting on the brakes just a tad while it was doing the shuddering as was able to keep the shuddering occurring while ever so lightly on the brake, so not as cut and dry as it seemed yesterday.

I also drove around a bit with the ECT in power mode and though it did not make the problem go away it certainly reduced the occurrence. Right around where I would get to the RPM, MPH, throttle position sweet spot for the shudder to occur it would be down shifting and putting me above 2K making the shudder go away.

https://drive.google.com/open?id=0B9PRGsVYG0KbT1AtcXdOSUU2SFE is a video with the speedo and tach while the shudder is happening.

 

I read the pm you sent to me .
I think you received some very excellent replies so far from the above members .
It,s everything I would have recommended and where I would start .
If your truck has 230k now , when was your last tune up ?
Spark plugs to start and while you are there , do a throttle body cleaning .
Disconnect battery for 1/2 hour for idle re-learn after throttle body cleaning .

If you still have a shudder after the tune up , then continue diagnosing but judging from your explanation I agree the truck needs plugs for sure . Its a cheap place to start

 

First I want to thank everyone for their feedback and help. I don't know shit and since I have a Tacoma that generally just runs and runs and runs with minimal interference and regular maintenance. This was the first time I had a concerning mystery on my hands and wasn't quite sure how to solve it.

So as of tonight the problem seems to be FIXED! I serviced the Air Filter, MAF sensor and throttle body. Then I replaced the spark plugs and wires. It was the first time I have done engine work on the truck and though a little nerve racking at times I got through it thanks to some good youtube videos, a whole bunch of threads and all mostly all of you making me think I could do it.

Tomorrow I will be putting some miles on the truck so I will get a better idea of if the problem has gone away but I couldn't get it to happen with a bit of driving tonight.

Thanks again and I will post if anything goes awry.