767Flyer,

If you want to find out if the caliper is causing the pads to drag, just jack the car up to get the wheel off the ground and try turning it. You can easily feel and perhaps hear a "dragging" sound.

This happened to my car once while on a long trip. The car started pulling very very badly to the right. When I stopped, I jacked the car up and found the right front wheel very hard to turn. I had found the problem!

Hope this helps. Let us know what you find.

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Ted
1979 240D
165,000 miles