That's right ... another driveline vibration

[hearingyourlies]

Alright guys, I'm just about at wits end, so i'm gonna be as thorough with this as possible.

Approximately 2k miles ago, while driving down the highway out of nowhere the truck started a low-decibel humming. At lower speeds, it went away (below 55).

Got home, my friend came over, we put it in reverse and drive several times and there was some serious clicking coming from underneath. Off to the mechanic, who removed the driveshaft, put in new universals, and slapped it back in. Clicking gone.

Guess what?! Above 55 mph, vibration persists.

Took it back, he suggested replace the yolk from driveshaft to transfer case. Guess what? Still there, and it seems to have actually made the vibration even more prevelant by tightening up the rear end slop.

All I'm left with is the thought that 1) I have a torque converter off balance hence the above 55 vibration or 2) the driveshaft is out-of-balance.

However, I don't want to start throwing money at this and I know this is a relatively common problem.

I have 78k miles, and the tires are perfectly balanced TOYO MT 35's. They have been on for almost 20k miles with no problems. Wear indicates no problems.

The vibration happens under load or not under load, in drive or in neutral ... so I really think that eliminates a transmission problem.

Any ideas guys? I'd really like to hear from someone that has solved this ...