I have an '87 sedan, and I'm wondering how to tighten the tension in the rear seat belts.
Thanks for all your help!

The post on cleaning the belts is valid, as a stiff belt would find it harder to go through the upper mounting point. Also, check that the upper point and lower point is aligned, i.e. the belt is entering the lower unit streight.

Having thought about this question some over the last few years, I've theorized the belts become stiff and dirty with age as opposed to any retractor springs getting weak. I wouldn't advise anyone to pull the spring end of their retractor to wind an extra turn or two, but I've had some good results giving the belts a nice warm bath and soft scrubbing. I used laundry detergent.

Here's a description of a repair I made a few years ago to the locking mechanism: click here

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Art Benstein near Baltimore

While we're on the subject...

I have an 81 242, and I'd love to know how to loosen the tension- or more exactly, adjust the sensativity. The seatbelt 'locks' at the slightest tug, making it almost impossible (for the non-expert) to get any slack out, or even to buckle up.

This used to be a luxury, affording me an excuse to reach across my date- but now I'm spoken for and its just annoying.

Retracting belts are designed to be mounted EXACTLY upright. The idea is that it would lock more easily when the car rolls, and possibly when stopping hard. If it is/was a bit loose, it might have moved slightly and is now more sensitive. Just loosen the bolt and turn it until you find it working better.