Darn, I am stumped

[punkncat]

Do me a favor and run it at that speed with tow/haul on. That will force the transmission into a lower gear and help us discern if the problem is in unsprung weight or driveline.

I was able to coax the manual shift into working. I feel no significant difference when in the "automatic" setting, or manual once it shift past 2nd into 3rd/4th with our without the torque converter locking. I feel this corelates to the speed 40MPH+ (too much) to call it a definite.
I am heading back up to my mechanic tomorrow to look at a thing or two and may run by the drive shaft place to see how inclined they are to take it out and check balance on it.

[ghilliesuit]

I was able to coax the manual shift into working. I feel no significant difference when in the "automatic" setting, or manual once it shift past 2nd into 3rd/4th with our without the torque converter locking. I feel this corelates to the speed 40MPH+ (too much) to call it a definite.
I am heading back up to my mechanic tomorrow to look at a thing or two and may run by the drive shaft place to see how inclined they are to take it out and check balance on it.

Balance the driveshaft seems like a good to start.

Did you / could you have a Road Force Balance performed?

Just an idea. I'm curious to know what fixes your problem. Good luck!

[Mr. Hick]

I was able to coax the manual shift into working. I feel no significant difference when in the "automatic" setting, or manual once it shift past 2nd into 3rd/4th with our without the torque converter locking. I feel this corelates to the speed 40MPH+ (too much) to call it a definite.
I am heading back up to my mechanic tomorrow to look at a thing or two and may run by the drive shaft place to see how inclined they are to take it out and check balance on it.

This is going to sound insane: I had a similar issue with a 2k11 Nissan frontier Pro-4x. It ended up being a broken leaf spring (center of the pack, at the axle). I ignored/chased/replaced/rebalanced double checked a million things before we found it. The only reason it was found is that my mechanic is anal and found a little bit of bright orange rust and wondered how and why it was there. I threw a $150 replacement pack in and the truck rode right immediately.

The fact that it's doing it regardless of the motor's RPM range but at that specific speed makes me believe that it's nothing to do with the motor. it's more likely suspension or drive line bearing issue. Have you tried getting the truck off the ground and on jack-stands (frame located) and pulling and reefin on stuff to see if anything is loose and worn (axle hub bearings, Differential bearings)?

[punkncat]

^Insomuch as possible I have jacked up wheels and felt for bearing play, etc. I can't tell anything is going on, but hopefully my man has the time and a free lift available to check out some things (further) in that fashion today. I am going to try and look closer at some of the suspension aspects. I think I mentioned earlier that I know I need struts but this doesn't act like a shaking strut at all. Maybe it is?

Thanks everyone for the suggestions so far. Will update later if we catch anything.

[punkncat]

So far as we can tell, it was a combination of two things.

The rear passenger side tire had thrown it's weight, apparently right after having them balanced about two weeks ago. In addition to that, it appears that one of the U joints in the rebuilt drive shaft may have shifted or not been installed 100% correctly. The rear section of the shaft is ever so slightly out of round in drive. We rebalanced and checked all the tires and I have to set an appointment to have the drive shaft spun up again.
Originally the thought was that I might have had water or a TPM sensor come loose in a rear wheel.

Just having half the equation done has made a significant difference but some of the vibration is still there. Will hopefully get that knocked out next week.

[martix_agent]

Glad you found your problems!!

[Mr. Hick]

Sounds good man! Shakes, wobbles and rolls can be a nightmare to correct.

[gabe]

My '12 Nissan Titan 4wd had a similar shudder when I got it in the same range and it turns out the driveshaft bolts were loose but it sounds like you already checked that.

The front wheel bearings on mine went out at around 90k miles and it developed a really annoying shimmy and whine above 40.

The usual drive related checks should be done. Check alignment, wheel bearings, tie rod ends, and rear axle links. Driveshaft bearings are sealed and non-serviceable on the Titans so just check for freeplay and if they're at all loose pull the driveshaft and have it overhauled and balanced. If the drive shaft is tight then it's easy to just pull the shaft, rotate 90 or 180 degrees and re-attach to the rear diff. Sometimes an ever so slight balance issue can stack between the rear diff and the driveshaft and manifest in a pretty good shake. Rotating the driveshaft in relation to the diff can change the harmonic node and that might tip you off to a balance issue.

[punkncat]

If the drive shaft is tight then it's easy to just pull the shaft, rotate 90 or 180 degrees and re-attach to the rear diff. Sometimes an ever so slight balance issue can stack between the rear diff and the driveshaft and manifest in a pretty good shake. Rotating the driveshaft in relation to the diff can change the harmonic node and that might tip you off to a balance issue.

Nice, may try that out right quick.