Looking for some ideas on a vibration with a new to me 84 300SD. Car has 118k on it, I've driven it about 3k now. Overall the car seems in very good condition. Almost everything works well and hasn't caused me any concern. I did recently replace the tires with new ones, motor mounts, engine shocks, and trans mount. I have done a valve adjustment, cleaned the banjo bolt to the ALDA, and plenty of other minor tuneups on the engine. New oil in the diff, the axle boots aren't torn or leaking and don't seem to have any issues I can tell so far.

On a recent trip, I noticed what felt like a vibration or hesitation from about 25mph to 30mph. After that, it smooths out and I don't think it comes back. I do get a vibration sometimes at about 70mph that comes and goes as well, not sure if they are related. One thing I did notice, the issue is much easier to notice if the rear of the car is weighted down, I had a full trunk on my last trip. This could have been occurring since I bought the car and I just noticed it after adding more weight to the rear.

I've searched the forum and most ideas tend towards the flex discs or driveshaft support bearing. Both flex discs look very good, and I haven't pulled the heat shield yet to look at the support bearing. But, I'd like to have some other suggestions to think about. I don't want to waste money trying new parts if I can help it.

Thanks