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I'm wondering that too, but I'm not a mechanical engineer. But if it was the flatness of the plate against the glass, I would think it would just crack around the hinge. It would seem to cause that explosion, there would have to be incredible pressure towards the middle of the hatch, from both the hinge area and rear deck area. I don't know for sure. But what's odd, a friend's (he's not on thirdgen) Formula hatch literally exploded as it was just sitting in the driveway. It was all original too. I don't get it.
Tempered glass does not crack. Once the "temper" is voided, the glass instantly breaks into a total shatter of small pieces.
Well I finally got the hatch glass replaced on my 1990 GTA. It's "new" (never installed) aftermarket glass. The protrusion of the rear deck is back but the upper part of the glass seems properly close to the roof line. Maybe the lower four holes in the glass, or even the upper four, are a few millimeters too far down. Who know? I just hope it doesn't shatter again! The bigger problem is increasing shaking in my left leg (lumbar damage from my career) which is making it hard, if not dangerous, to drive a clutch. This GTA (1990) is just 1 of 78 built with a 5 spd. Might have to let it go, look for another Gen III w/an auto transmission (egad!).
Well I finally got the hatch glass replaced on my 1990 GTA. It's "new" (never installed) aftermarket glass. The protrusion of the rear deck is back but the upper part of the glass seems properly close to the roof line. Maybe the lower four holes in the glass, or even the upper four, are a few millimeters too far down. Who know? I just hope it doesn't shatter again! The bigger problem is increasing shaking in my left leg (lumbar damage from my career) which is making it hard, if not dangerous, to drive a clutch. This GTA (1990) is just 1 of 78 built with a 5 spd. Might have to let it go, look for another Gen III w/an auto transmission (egad!).
The sensations are always present. The shakes comes and go. I didn't take a new pic of the glass reinstalled...doesn't look any different than any of the others but here's a few oldies!
I’m currently in the process of replacing my shattered glass (over torqued the hawks hinge bolts) with the optic armor polycarbonate, and now need to drill the holes for the hinge and hatch bolts - I’m trying to keep the hatch functional. Anyone here ever make a template or take measurements for the hole locations?
I’m currently in the process of replacing my shattered glass (over torqued the hawks hinge bolts) with the optic armor polycarbonate, and now need to drill the holes for the hinge and hatch bolts - I’m trying to keep the hatch functional. Anyone here ever make a template or take measurements for the hole locations?
I had inquired at Optic Armor and they told me polycarb wasn't suited for "daily use." Kinda got a brush off from them. I hope it works out for you. Yes, with the Hawks at hinge to glass you gotta go hand tight and 1/2 turn max...way below factory spec. I am unaware of any templates for drilling the holes, sorry. I'm currently trying to find out if there's a light pressure hydraulic clutch. Mine is a rare (1 of 78) 5 spd but due to back issues my left leg shakes horribly and it's almost at the point of being unsafe to drive my GTA. Might have to sell, look for one with an auto trans.
I had inquired at Optic Armor and they told me polycarb wasn't suited for "daily use." Kinda got a brush off from them. I hope it works out for you. Yes, with the Hawks at hinge to glass you gotta go hand tight and 1/2 turn max...way below factory spec. I am unaware of any templates for drilling the holes, sorry. I'm currently trying to find out if there's a light pressure hydraulic clutch. Mine is a rare (1 of 78) 5 spd but due to back issues my left leg shakes horribly and it's almost at the point of being unsafe to drive my GTA. Might have to sell, look for one with an auto trans.
the word hand tight on glass gives me ANXIETY!!!!!!!!!!!!!!
the word hand tight on glass gives me ANXIETY!!!!!!!!!!!!!!
ugh lol
Well.........there's 57 year old broke down me hand-tight.....then there's Arnold Schwartzenegger in his youth hand-tight!! Anything with these hatches gives me anxiety LOL. They're so problematic and GM knew it all along.
Well.........there's 57 year old broke down me hand-tight.....then there's Arnold Schwartzenegger in his youth hand-tight!! Anything with these hatches gives me anxiety LOL. They're so problematic and GM knew it all along.
I imagine his "finger tight" is like 536 foot pounds lol
Back in high school, my classmate hand tightened" honda Accord Valve cover bolts using a 1/2 inch drive large breaker bar...the bolts were like thinner than a pencil and he snapped them off lol Our teracher went nuts and started yelling at him.....luckily back then there were a ton of Accords in the junkyard and we found one easily!
I keep remembering that whenever I "hand tighten" something
LOL too funny. Yea, finger tight or hand tight can me a lot of things.
On my project, I apparently left some of the hatch glass bolts loose 9I was trying to get that rusty one off...)and forgot to tighten the others I was able to loosen... I saw that it slid a bit as I opened it... i nearly soiled my pants!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
I may have discovered why the rear deck windows in our gen-3 Camaro’s are prone, over time, to breakage.
…And I believe the problem is not due to the glass itself.
Let me explain:
HINGE MOUNTING:
There are a pair of hinges that attach the rear hatch glass at the roofs rear edge.
Each hinge has two through bolts attaching the glass via oversized clearance holes in the glass.
A butyl rubber is used between the hinge bolt outside-diameters and the oversized glass hole inside-diameters.
The butyl rubber is also placed between each hinge plate surface and the glass surface.
Once the hinge bolts are torqued - I believe the factory thought the glass would never move relative to the hinge.
And it probably won’t, for a while…
LOWER HATCH & SPOILER ASSEMBLY MOUNTING:
Similar to the top hinges, the lower hatch panel attaches via studs and oversized holes along the lower edge of the glass.
Again butyl rubber is used to isolate the stud outside-diameters from the glass hole inner-diameters.
A strip of butyl rubber is also run along the length between the glass and lower hatch panel to keep water out and to create a mechanical bond between the two.
Once again, after the stud nuts are torqued the glass is meant not to shift.
Similar to a front windshield installation which also uses butyl rubber, I believe the factory thought the hatch panel would not move relative to the glass.
BAD INDICATORS:
My Camaro’s gap between its roof and glass at the upper hinges is 3/8” larger than meant to be.
And my lower hatch panel rear-most edge extends 7/16” beyond the rear quarter panel ends.
(Note: my z28 is a no-hit car and I seriously doubt it ever left a GM assembly plant with these gaps).
PROBABLE FAILURE MODE:
With the Camaro rear hatch in its closed position both hatch gas-struts are fully compressed.
This means, when closed, the struts constantly exert their maximum force against the lower hatch panel attaching brackets.
Which means they are constantly pushing the lower hatch panel rearward. Strut force is also passed back through the glass and both upper hinges.
The pivoting end of the hatch struts are mounted to brackets attached to the body structure near the top of each rear seat.
Over time the gas strut force distorts the pliable butyl rubber at both the upper hinge and lower hatch panel mounting locations.
This distortion causes the hatch assembly to increase in length (via butyl rubber creep) until the hinge bolts and panel studs come into contact with the oversized glass holes.
Once the bolts and studs contact the glass holes movement (creep) stops.
(Indicated by larger gaps at the upper hinges and by the lower hatch panel extending beyond the rear quarter panels).
With mounting bolts & stud diameters directly contacting the glass hole diameters the glass is stressed at these contact points.
While under stress, any adequate temperature change, shock or twisting of the glass could cause it to shatter.
THE FIX:
Disassemble and reassemble the entire hinge/glass/lower panel using existing best practices that will assure the mounting fasteners no longer contact the glass clearance holes.
Design and install 2 custom made gas-strut brackets that will bear the compressed strut loads instead of the lower hatch panel in the closed position.
Very thorough analysis. Yes, I think there's something to ensuring the metal through bolts upper and lower don't directly touch the glass. RTV, pipe thread tape, anything. I did see on a FB group that GM had to go to the hatch pull down motor in 85 due to hatches shattering when closing and there is video of a hatch shattering on the assembly line. We are probably looking at a combination of things. I do think GM erred in putting such a big heavy, unsupported piece of glass on the back of the III's. So far my replacement hatch (new glass) is holding but I'm being very careful also. Although the upper alignment is factory-perfect still, the lower lip once again protrudes about 1/8" or so past the back. I don't know if the glass shop made a mistake in reassembling the hatch, or if the after market glass lower bolt holes are slightly too far down. Sigh.
The thing I don't get about the decklid theory... or rear decklid misalignment in general... is that the black trim that's on the glass screws directly into the decklid...yet the decklid still gets out of alignment...
Definitely something of a mystery. Assuming all the Gen III's had the lower four holes for the glass to be secured to the deck, there's no way it would stretch out. I still think the culprit there is the hinges sagging and bending.
12-14-2021, 02:50 AM
is it a constant shake? 
