Seat belt mechanism - how does it lock?

[Barbecue]

Hey guys,

I have a quick question about the seat belts in my '86 Silverado. From what I understand, the seat belts on our trucks the same 1978 and up. The seat belts I have are the single box units beside the bench (retractable shoulder belts).

My question is, if I'm in an accident, what mechanism (what action per se) actually locks the shoulder belt?

The reason I ask this is that with other older vehicles I've worked on, if you yank on the shoulder belt, it locks. This is basically simulating a person's torso lurching forward in an accident. When I yank on the shoulder belts in my truck, the belt do not lock. The belt themselves do retract, albeit a little weakly. Is there some other kind of mechanism, perhaps a pendulum or something, which locks the shoulder belt in the event of a crash?

Thanks in advance for any insight you can offer. I'd just like to have the confidence knowing that my passengers (and I) are safe.

BBQ

[Just call me Sean]

Yanking does not lock the seat belts. They work from centrifugal force, a pendulum.

[Barbecue]

Originally Posted by Just call me Sean

Yanking does not lock the seat belts. They work from centrifugal force, a pendulum.

Thanks for the quick reply, Sean. What's the simplest way to test them? Perhaps perform a hard brake and lurch my body forward to see if they lock?

I normally wouldn't be so concerned as my truck is in overall great shape, but all of the problems I've had to correct have been related to the truck sitting unused by the previous owner for the past year. I've basically been fixing items which have deteriorated due to neglect. I just don't have much trust in seat belt mechanisms which have sat unused for a period and would love to test them to have confidence.

Cheers!

[Just call me Sean]

You could slam into a wall.

[tucsonjwt]

You have asked one of the great unanswered questions of my life: How do you know if these old square seat belts are working if you can't yank them to find out? My 83 seems to be different from the 78 I had. The 78 had some kind of weight in the B pillar behind the seat which would make a clunking noise periodically when in motion, so I assume that there was some sort of weight in there to activate the lock mechanism. My 83 makes no such noise. Neither of these truck had belts which could be tested by yanking. All of my other vehicles can be yank tested.

Someday I will replace my seat with a pair of Sebring convertible seats which have nice "yankable" integral seat belts.

[tylervalo]

There is a pendulum, i found out when my new carpet was pressing against the rear plastic housing pressing the pendulum forward and not letting me put the seat belt on. I remedy'd the issue by cutting the rear plastic piece out of the seat belt housing.

[jetmech85]

Try pulling on the belt while doing a firm braking on an open road. That should swing the pendulum enough to lock the belt. Really a simple design but not something I could ever dream of. GM engineers must have had a lot of free time.

[Barbecue]

Thank you, everyone, for the detailed replies and insights. I feel much better now knowing it is a pendulum mechanism. I'll do as you suggest, jetmech, and give 'er a test.

Cheers!

[motornut]

they lock with the door closed,the release is when opened the white plastic button in the pillar,pops out.check that moves

[Just call me Sean]

Originally Posted by motornut

they lock with the door closed,the release is when opened the white plastic button in the pillar,pops out.check that moves

Fords do that. I'm going to check my truck when I get home but pretty sure Chevys don't.