My car is an '87 Euro 300D, and the rear doors are difficult to fully open, mainly because they are rarely used. And they make a lot of niose while being opened.

I tried lubricating the guides, balls, and springs with good grease. It has improved a bit. But after a month, the doors are back to the same old "hard to open" condition.

Guys, it seem so simple, but I can't seem to fix it. How is this problem corrected?

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Jake