TCC Slip Speed or Torque Convertor Issue? (SOLVED, Drive Shaft Pinion Angle)

[gmartin1215]

I rode in the back while having my son drive around, and put my ear to the floor. I am hearing that problematic niose coming from the rear diff (like a high-pitched rumbling/buzzing ringing). When I am driving, almost seemed like the noise was coming from transfer/transmission area.
Anyway, I am taking the truck back to the diff shop next week to have them evaluate the rear to make sure all there is good. At least, remove this variable. If all good there, then I will take the truck to a reputable 4x4 shop to have them see if they can determine the cause for the noise (could be pinion angle is causing the vibration/noise - I'll do my own checks here, but they may be able to better dial it in). The reason I'll do this step is that the diff guy knows diffs, but when it comes to lifted 4x4s, he admits that he is not an expert at eliminating driveline NVH.
If all good here, then I'll go back to exploring if it is the TC and/or transmission. But what I have tested so far seems to indicate I am OK here, except for the high mileage on the unit. I am due to have the transmission serviced, so probably will be a good time to take it to a shop and have them do a full diagnosis to see if they indicate anything that needs attention.

Ugh! I hate chasing noises, but at least learning what it needs and doen't need along the way.

As always, I appreciate all the tips/advice provided by this group!

I took the truck back to the shop that did the re-gearing because I was hearing a rumbling sound from the rear diff. I wanted that shop to verify the re-gearing work was OK. They put it on a rack to run the truck at different speeds and determined that the sound/vibration was coming from the transfer case, with the diff OK. After a discussion with the owner about what he found, he said that he strongly beleived it was the pinion angle was off. He had tried to adjust it previously, but admitted he was not an expert in this kind of alignment on lifted trucks and recommended I take it to a specialist.

I went to a 4WD specialist shop, described my issue, and outlined all the work that had been done. They tried adjusting the pinion angle and were able to improve the issue a little, but with my lift, if the angle was off by 1 degree, the problem would come back. With my lift, I was not going to abe able to get 100% in the sweet spot for the pinion angle, and I will still get the the sound/vibration as I coast/load the axel, and the axel rotataes (though the control arms stabilize the axel rotation a lot, there is still some that would put me out of the tight margin for the pinion axel). Given this situation, the recommendation was to upgrade to a double-cardon drive shaft. I decided to give this a try.

The 4WD drive had the drive shaft built and installed on my truck, and they adjusted the pinion for the CV joint (pinion angled directly at the transfer case). After the install, they drove the truck on the highway at various speeds, then called to say they had remedied the problem. After I got it back, I did my own tests to try to replicate the sound/vibration where I detected it. Sure enough. Upgrading to the double cardon drive shaft solved that sound/vibration issue! I'll do a separate write-up for the lifted Tahoe section, so anyone looking to build one can find this information.

With this problem solved, I can pay more attention to my transmission and transfer case. Each has 160K on them so I know I am in that area where these parts tend to fail. I am getting a slight pause between 1st and 2nd gear, but everything else seems to shift OK. My guess is the torque converter may be getting a bit worn, and when I did the parking brake stall speed test, I may have worn the clutch down a bit. Not sure yet. I probably will take it to a tranny shop to have them service it and go through the transmission as much as they can to see if they can detect any potential failures.

Anyway, one headache down. Goes to show that when you upgrade/change something, something else will likely show!