76 Seat Belts Questions

[74CustomK20]

My 77 cab had a 3-point seat belts. Didn't work worth the fabric they're made of. I got a set of 73 lap belts (oddly enough orange so they matched my interior) but have been reading that in 76 3 point became mandatory. True? But I have also heard of some with post 76 squarebody's with only lap belts... Anyone want to elaborate?

[JWall]

My 76 came factory with lap belts only.

I'm sure Keith or others can give more of the specifics on wha years the changes were made.

[cadillac_al]

My 76 GMC came with lap belts too. I'm pretty sure 76 was the last year. It's kind of a pain when you have to explain it to younger cops.

[Axle]

Mandatory in passanger cars.

What does your lap belt buckle look like? Is there a keyhole slot in it? If there is and you'd like to add shoulder belts you'll need to find a shoulder belt from a 1973 model year car or truck (and 1974, but that is more hit 'n miss since things started changing up again when it came to seatbelts).

Alex.

[74CustomK20]

The shoulder belts are a pain in these trucks so rather just stay lap. I only drive it... 5? 6 tops a year so it's not really a big thing just gotta make sure johnny law is happy. Now just curious if my 74 cluster will work with my 76 wiring...

[74CustomK20]

Curious more still, what about a 77 with only laps, anyone know? Like a issued truck to military or somethin?

[ray_mcavoy]

Originally Posted by 74CustomK20

Now just curious if my 74 cluster will work with my 76 wiring...

Warning lights or gauge clusters?

If they're both warning light clusters, it'll be a direct swap.

If they're both gauge clusters, you will have to deal with ammeter vs. voltmeter issues. Do not plug a 73 - 75 gauge cluster with an ammeter into a 76+ truck that's wired for a voltmeter ... it will create a short circuit. One option would be to change the wiring to work with the ammeter. Another option would be to replace the ammeter with a voltmeter ... that can usually be done with minor modifications to the cluster.

Converting from warning lights to gauges will require re-pinning the cluster connector and making some changes to the wiring.

[74CustomK20]

My motor has a guage temp sensor, and a mechanical oil guage. I'm buying the wiring harness from old rusty c10 front to back out of a 76 c10. So I'm not sure. I have a CAB 74 harness in great shape. What would be needed to use the 74 with the 76 motor back and front? I have a 74 cluster with no guages in it but it had guages before. I have all but the ammeter to put in it... If that all makes sense.

[ray_mcavoy]

Originally Posted by 74CustomK20

I have a 74 cluster with no guages in it but it had guages before. I have all but the ammeter to put in it... If that all makes sense.

Okay, so you basically have all the parts (minus the ammeter) to assemble a 74 gauge cluster. Or looking at it another way, you could swap in a voltmeter (with some minor mods) and basically have the functional equivalent of a 76 gauge cluster.

If you stay with an ammeter, you could use your 74 cab harness as-is (assuming it's for gauges and not warning lights). Then you'd have to add in the necessary ammeter wiring to the 76 engine harness. And to be on the safe side, compare the 74 vs. 76 wiring diagrams to make sure all the other wires in the bulkhead connector stayed in the same locations.

If you change to a voltmeter you could use the complete set of 76 wiring harnesses as-is so long as they came from a truck that originally had gauges.

[74CustomK20]

Well... It really makes me no difference... So long as I have a working cluster! Haha. Which is easier or more reliable? Or has less headaches later on?

Edit: after a search I seen where its MUCH easier for a volt guage. Which 2 wires need swapped on the cluster plug? That I have not found... Guess I will try n label my truck a 76 then... The wiring will depend on which parts truck I will try n find for the rest of it...

[ray_mcavoy]

In that case, I'd recommend going with a voltmeter. It'll be easier to wire up (no changes if the 76 harness is for gauges). It'll give you more info about the state of the battery/charging system. And you won't have to deal with any issues regarding the ammeter's max current capacity if you use (or plan to use) a high output alternator.

But if you do go with an ammeter, be sure to use 4A inline fuses in the engine harness portion of the ammeter circuit as shown in the 73-75 wiring diagrams. They're an important part of making the circuit safe.

[74CustomK20]

Voltmeter and a 76 truck it is! I know everything swaps. But when thinking of what parts come from where it makes it helluva lot easier when ordering parts!