Well, after pulling the exhaust system a few times to get at the driveshaft and try different things, I have GREATLY reduced the drumming, thrumming vibration in my driveshaft. After going through all this, if I had it to do over again I think that I could have fixed it in fifteen minutes if I had known then, what I know now.

After pulling down the driveshaft, some time ago, to replace the front flex disk, I picked up the vibration. I had some tire problems at the time, so I didn't confirm the driveshaft vibration until I sorted out my tire problems which was a broken belt that was hard to find.

After the tire problems were taken care of, I thought that maybe I had not gotten the shaft splined up correctly, so I pulled the exhaust to check. I had indeed marked it and everything was cool. Since then I learned that there are permanent marks on the front and rear of the shaft from the factory, and they were indeed aligned properly.

I tried following some factory info, that said to unbolt and turn the shaft 120 degrees at the transmission and try it again. That did nothing. I then bought a transmission mount thinking that maybe it had come down some causing a bad angle. At the same time I got a carrier bearing and support and a rear flex disk. With all these parts on hand I was ready for the attack.

I got all these parts and pulled down the exhaust and shaft yesterday. The transmission mount was indeed much softer than the new one, and the rear flex disk was pretty cracked, so I put in the new parts. With the driveshaft out I was able to spin the carrier and evaluate it better than when in the car. It seemed in real good shape as did the support.

While the shaft was out, I rotated the u-joint on both axes. The joint had a "detent", or a notch in the center. It seems that it must be worn in that specific position in which this joint almost always stays. In these cars, the shaft probably never flexes over one degree, so the joint only wears in that specific spot. In fact, I really think that once you pull down the shaft, flexing the u-joint some 15 or 20 degrees, you might be causing something to happen inside those bearings because you are moving them out of their wear zone. Maybe this somehow causes the "detent" to occur.

I removed the harmonic weight while I had it apart, and before reassembling, I cleaned and greased the splines and the centering bushings and pins on both ends of the shaft.

I put everything back together and road tested. I could tell no difference.

With knowledge of the "detent" in the u-joint, I decided to move the carrier bearing position slightly to see if running the u-joint through a different arc might make it happy, and it did.

By taking loose the three 8mm screws on the converter heat shield and rotatiing it to remove, I had access to the carrier support. I loosened the vertical bolt on the drivers side and removed the one on the passengers side that is at an angle. I put a few washers between the carrier support and the chassis mounting hole, then put the bolt back in and tightened everything up.

After putting the heat shield back in, I was done. It took about fifteen minutes. I don't think the vibration is 100% corrected, but it is almost completely unnoticable.

There are two possible lessons here; the first, don't pull down the u-joint causing it to flex beyond it's normal angle unless absolutely necessary, secondly before going to all the trouble of removing the exhaust et al, try slightly changing the position of the carrier support to see if the vibration goes away. You can do it in fifteen minutes. It's worth a try.

I'm very relieved as I was beginning to think that I would have to buy the rear driveshaft portion for over $500. That's the only way to replace that u-joint. Given my recent career woes, that was not a very attractive alternative.

Sorry for the lengthy post, but I thought that it might help someone who is living with driveshaft "thrumming."

Have a great day,