Ryan:

Yes, a good road trip under heavy load will do wonders for a diesel. My 300D was still knocking and running rough after the IP repair until I drove to Miami for Christmas (I waved as I drove past!) -- no noise at all now, and runs very smooth. No smoke, either, but then it never really made any.

There are several sources for the front end noise:

1. Loose wheel bearing, or worn bearings. This is most likely as there is play -- check by pulling straight out with the wheel off the ground. If the wheel moves straight in and out with a perceptible thump, the wheel bearings are loose. Adjust them and the problem will go a way. Will also make the car wander a little, more as they get looser.

2. Worn tie rod ends, drag link, or pitman arm joint. If these are worn, there will be no movement directly in and out with the wheel off the ground, but you will have a perciptible thump if you rotate the wheel on the steering knuckle, or hold the wheel and turn the steering wheel. You can usually tell which part is worn by looking for relative motion between the tie rods and what they attach too. You can also put you hand on them and feel smaller motion. Fairly easy to fix.

3. Worn ball joints. If you can't find any looseness in the wheel bearings or steering system, pry straight up and down between the tire and the ground -- any significant movement or thump indicates worn ball joints. This is a big pain, and expensive.

4. Worn track rod bushings (on the frame) or bearings (on the control arm) or worn control arm bushings. Usually causes a groan when you go over a dip in the road, or any other time there is large suspension travel.

5. Worn roll bar bushings. These are up along the firewall, above the tire. If they are bad, the roll bar can vibrate at certain speeds. Will also cause a thump when you drive over speed bumps at an angle, or hit a small bump in the road with one tire.

The other possibility is bad shocks -- this won't cause any play in the suspension, though -- will permit up and down vibration of the wheel at certain speeds and will beat the tire to death rapidly. Check for cup wear on the tire -- any evidence of cupping and I'd replace the shocks.

This should get you started!

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!