mibars
Full Access Member
- Joined
- May 13, 2023
- Posts
- 268
- Reaction score
- 439
- Location
- Nadarzyn, Poland
- First Name
- Michal
- Truck Year
- 1990
- Truck Model
- Suburban V1500
- Engine Size
- 350 TBI
My right middle row seatbelt in 1990 Burb was not retracting due to rusted parts. I didn’t find much details online so I used this occasion to look inside and document it for whoever may need in the future.
The cover can be removed by unclipping bottom part which swings open and then by yanking on it upwards. It will stay on seatbelts.
The cover doubles as a seatbelt guide, so any misalignment may cause seatbelts to not retract correctly as the retractor springs are barely capable of retracting the belt itself.
To remove the seatbelt you need a T50 bit. Mine was rusted solid so I had to drill it out. Seatbelts threads into an oval reinforcement plate. This plate is welded in 2 points to the body. If you remove it you’ll end up with one large and 2 small holes in your body. Seatbelt mounting bracket is surprisingly flexible and looks like it’s designed to bend if yanked hard enough, acting as a crude force absorber in an event of a crash.
Operation is quite simple, there are two individual reels, each acts independently. G forces or tilt affect hanging weights which swing and lift the locking bar up against the ratchet teeth. There is no mechanism to activate the seatbelt by rapid unspooling like in modern seatbelts.
The black and pink mechanism in between spools was malfunctioning in my seatbelt so I took it apart to investigate. It looks it’s sole function is to provide a child seat lock. Once the lap spool unwinds almost fully it moves a tiny lever that lifts the locking bar against the ratchet. It then allows only retraction of seatbelt, so you can mount a child seat with a tight lap belt. To disengage that function you must allow a lap belt to retract almost fully, it then moves the lever away from the bar allowing it to drop down. Even though both spools seem to engage with that mechanism via pink gearbox I see that shoulder belt has zero effect on operation of a lap belt lock.
There is a minor difference between spools in a way the belt is wound: Lap belt is spooled directly onto metal spool, while shoulder belt has an additional plastic spacer increasing the diameter of a spool. I have already removed it before taking picture, that's the off white tube with a spline inside.
The “do not remove” covers hides clock springs, tiny and weak compared to modern ones. It is possible to carefully remove cover with a spring without causing a mess, one needs to unclip and unwind it while still connected to the spool. Mine took 10 rotations before it bind against plastic cover, then it can be removed as an assembly.
The spool is not removable from the cage, it is secured by components that were pressed together and bent. The belt is most likely removable from the spool, I didn’t bother to try that.
In my case the rust was creating enough friction to stop the spring from retracting the shoulder belt. I cleaned and greased it as much as I can, followed by two simple tricks to increase the retracting force: I gave the spring two additional rotations to increase spring preload and omitted the plastic splined tube on a spool to decrease it’s effective diameter, making it retract less per rotation, but with slightly increased force. I tested it and the spool can still retract fully without the spring binding. I also didn’t reinstall the child seat locking mechanism which has some broken pieces:
The outcome is that now I have a seatbelt that is once again usable, does retract and locks correctly with G forces, although does not have a child seat functionality. Better than non-functional seatbelt.
As this is safety feature please take this writing as “for information only”. Do not follow for your own and others safety. Replace seatbelts with a new, working unit only. Do not microwave, may contain peanuts.
The cover can be removed by unclipping bottom part which swings open and then by yanking on it upwards. It will stay on seatbelts.
The cover doubles as a seatbelt guide, so any misalignment may cause seatbelts to not retract correctly as the retractor springs are barely capable of retracting the belt itself.
To remove the seatbelt you need a T50 bit. Mine was rusted solid so I had to drill it out. Seatbelts threads into an oval reinforcement plate. This plate is welded in 2 points to the body. If you remove it you’ll end up with one large and 2 small holes in your body. Seatbelt mounting bracket is surprisingly flexible and looks like it’s designed to bend if yanked hard enough, acting as a crude force absorber in an event of a crash.
Operation is quite simple, there are two individual reels, each acts independently. G forces or tilt affect hanging weights which swing and lift the locking bar up against the ratchet teeth. There is no mechanism to activate the seatbelt by rapid unspooling like in modern seatbelts.
You must be registered for see images attach
You must be registered for see images attach
The black and pink mechanism in between spools was malfunctioning in my seatbelt so I took it apart to investigate. It looks it’s sole function is to provide a child seat lock. Once the lap spool unwinds almost fully it moves a tiny lever that lifts the locking bar against the ratchet. It then allows only retraction of seatbelt, so you can mount a child seat with a tight lap belt. To disengage that function you must allow a lap belt to retract almost fully, it then moves the lever away from the bar allowing it to drop down. Even though both spools seem to engage with that mechanism via pink gearbox I see that shoulder belt has zero effect on operation of a lap belt lock.
There is a minor difference between spools in a way the belt is wound: Lap belt is spooled directly onto metal spool, while shoulder belt has an additional plastic spacer increasing the diameter of a spool. I have already removed it before taking picture, that's the off white tube with a spline inside.
You must be registered for see images attach
You must be registered for see images attach
The “do not remove” covers hides clock springs, tiny and weak compared to modern ones. It is possible to carefully remove cover with a spring without causing a mess, one needs to unclip and unwind it while still connected to the spool. Mine took 10 rotations before it bind against plastic cover, then it can be removed as an assembly.
The spool is not removable from the cage, it is secured by components that were pressed together and bent. The belt is most likely removable from the spool, I didn’t bother to try that.
In my case the rust was creating enough friction to stop the spring from retracting the shoulder belt. I cleaned and greased it as much as I can, followed by two simple tricks to increase the retracting force: I gave the spring two additional rotations to increase spring preload and omitted the plastic splined tube on a spool to decrease it’s effective diameter, making it retract less per rotation, but with slightly increased force. I tested it and the spool can still retract fully without the spring binding. I also didn’t reinstall the child seat locking mechanism which has some broken pieces:
You must be registered for see images attach
The outcome is that now I have a seatbelt that is once again usable, does retract and locks correctly with G forces, although does not have a child seat functionality. Better than non-functional seatbelt.
As this is safety feature please take this writing as “for information only”. Do not follow for your own and others safety. Replace seatbelts with a new, working unit only. Do not microwave, may contain peanuts.
