'85 300TD rear drive/wheel clunking
 

I posted about this a while back but never looked into the issue.... my wagon is experiences a scraping/clunking noise from the rear right wheel area. Its only after driving for at least an hour and at 65+ mph. I used the car as a daily driver for 45 miles one way for six months, never hearing a problem. But once I hit the highway for a road trip, the scraping/clunking only occurs when already driving a while.

I also notice that it tends to go away as soon as I let off the gas. Coasting there is no noise.

So far as soon a I park, then hit the road after a few minute break, it goes away for a half hour maybe or more.

I resealed and cleaned the brake calipers and otherwise don't know what is causing this. Might it be brake related? I don't know if the rear wheel rotates freely or if the brake caliper is acting up still. I'm wondering if its maybe a drive axle problem?

My predicament is that I'm moving 250 miles away and hope to get the car driven to my destination.... right now its my only drivable car since my sedan has a rusted torn rear suspension arm. Until I get that fixed I'm hoping my wagon can at least go the one trip then handle errands until I get the sedan's rear suspension swapped.

Any ideas what the wagon's scraping/clunking might be? Might it be internal gearing or torn teeth on the driveaxle somewhere? I have a rear differential and the axles from a 300SD but don't know if those are compatible... I think the SD is a bit wider based than the TD.

Someone before suggested that the boots may be torn and the axle need decreasing, as long as its not damaged yet.... I'm on the road now and hope it'll go another 150 miles home.

could be cv joint. Put the car in a position that you can get under it with itin neutral and fixed so it will not roll over you and reach up and try to wiggle the half shaft up and down. It should slide in and out a bit but not up and down at all. Also look at the rubber boot. If the boot is bad dirt can get in and will soon ruin a good cv joint. the cv's don't last forever but they do last a good long time if kept clean and lubed.

ok... there are a few things that could be causing this. axle is one, but the differential is another. also, the swaybar links can plop down and hit things making noise.
SECURE the vehicle, and raise the rear up, and pull the fill plug on the diff. stick your finger in there and see if it's got clear fluid in it. *(Careful! if you've recently driven anywhere, the oil will be HOT) check the axle for play as suggested by t walgamuth.