Hello. The rear hatch shattered today on my 1990 TA GTA (see pic). I could use help in finding a replacement. Since finding a salvage 30 yr old piece of glass will likely just result in another stress shatter, if anyone knows of a source for polycarbonate replacement glass please let me know. If it weren't for bad luck, I'd have no luck at all. I'm in Palm Beach Co, FL.

 

www.opticarmorwindows.com

I've been thinking of getting their lightweight hatch myself.

 

Thank you!

 

how did it shatter???

 

Literally, just driving slowly over one of those speed humps. Must have put enough angle on the chassis to stress the glass.

 

Ridiculous. I wonder if tempered glass gets more brittle with age.

 

I suspect so. My buddy's Formula had the rear hatch shatter just sitting in the driveway.

 

Any downsides to that polycarb option?

 

I contacted one company that said GM went back to glass because of cracking and warping with polycarbonate or other plastics.

 

I've worked with polycarbonate quite a bit and I can't see it cracking. -other plastics yes. ....but warping is another issue. As big as that hatch is....I can see that potentially being problematic.

 

Maybe polycarbonate works best in flat panels then? I don't expect that any glass companies make brand new tempered glass hatches for a vehicle made in 1990. I'm sure there are salvage hatches out there....but I worry that a 30 yr old piece of glass is still going to have problems with shattering. Waiting on a call from my insurance company to even see if this is covered.

 

If it makes you feel any better, most of us out there don't have issues with the back glass. Without doing any research, I think the glass should be find, generally speaking. Now if there's a specific reason yours popped, well that may be a different story. I know the hatches tend to get out of alignment, and I can see that being an issue.

 

Just put new Hawks hinges on it and got it aligned properly a couple of months ago. By the way, those Hawks Motorsports aluminum billet hinges are phenomenal and well worth the money.

 

remember, these are used in conjunction with the factory steel frames, and as long as you don't park it in the arizona sun day after day, these work quite well. the armour coat is a must, lexan and other plastics scratch irreparably without it. if you use the 18% tint, they can be made to look completely stock, and when used with a fg trunklid, the weight saving is between 70 and 80 pounds.....

 

Thanks for the info. I don't know if insurance will go for a polycarbonate replacement but we'll see. Glass may be impossible to find. Cleanup is sure a pain. A million pieces of glass!

 

Been exploring replacement glass over the past couple of months and about the only thing available new is the windshield and door glass and that's depending on who you talk to. New rear (OE type) is not available from anywhere that I've found.
Hawks has take off glass available as I was going to go with a rear glass from them until my home A/C went out and the wife's car needed attention as well. Will that polycarbonate deal with the weight/stresses like the OE glass does? With steel hatch and aero wing I'd be concerned about that.

 

I can't find any rear hatch glass on Hawks. Can you post the link. I got the aluminum billet hinges from Hawks. They're awesome.

 

Hawk's has a gazillion cars just sitting in the yard. LOTS of various used parts not listed on the size. Just give 'em a call.

...I'm definitely interested when the time comes. Good to know about the armour coat.

 

You'll have to call them as it's a used part and they have a large inventory of cars to pull from.

 

Thanks. I did see one hatch (glass/wing) but for a Gen IV listed. I know they have lots of salvage cars. I just shudder at the shipping costs from Easley SC to S. Florida!

 

I heard people question if the aluminum hinges from HAWKS has somehing to do with the glass breakage???

 

I have not heard that. What I did see was a lot of rave reviews for the hinges. They're supposed to be an exact replacement and certainly appeared identical. Aluminum would not be a factor.

 

That's what they said here too. I was going to get some but now have huge doubts about it.....

But there is speculation that the hinges maybe aren't machined perfect, maybe torque specs etc.... or are installed on wrong sides etc......basically a lot of unexplained "exploding" hatches shortly after hawk's hinge install



Chronic Hatch Glass Breakage - Third Generation F-Body Message Boards

 

Now that is too much coincidence. Seems a lot of people have had unexplicable explosions of the glass right after installing the billet hinges. I'm going to order OEM and go back to that just in case. I don't see why that would make a difference unless the glass part is flat and totally inflexible and the steel gives a little. I'm not a metallurgist so I don't know. Thanks for the information though.

 

i have the billet hinges from HAWKS, very cool pieces, perfectly done. IF the glass breakage coincides with hinge change, it's the change that's the problem, not the hinge, and IMO that goes for billet or stock. That's a huge, heavy piece of glass with complex curves, and it rides on two puny hinges, and one latch. I always change out the seal when i change hinges or glass, i think that one of the reasons the new cars didn't have this problem is bc the heavy glass has much more support from a new seal. those things shrink and warp over time and the irregular support from them over time contributes to the glass break potential

 

Follow up questions. First, what is "the seal" you're referring to? Do you think there is anything to the notion that the rear deck is pushed backwards off of the glass accounting for the gap and in my case, the contacts for the 3rd brakelight not meeting? Do you think GM originally designed the hinges with the bow we see in some of the pictures above, or is that purely bending from age and stress? Finally, is there still a source for OEM steel hinges? Everything I see is the same aluminum billet hinge Hawks sells. TIA. Here is the link to a big thread on this same issue: https://www.thirdgen.org/forums/body...-breakage.html

 

I think he is referring to the seal that goes al around the hatch opening. The weather-strip basically.....


They said that the hinges from GM are marked Left / Right. Which means they would differ....
Are there any differences / markings for the HAWKS hinges? Or are the both the same?

Also, what torque spec did you use to tighten them? theres another thread aout that as well.

 

Hatch alignment and paint + aero wing - Third Generation F-Body Message Boards

 

Torque was possibly factory (shop did the work)...but I did see on Hawks just now hand tight only. Can't get a good answer on whether original hinges came bowed or flat like the Hawk's ones. Nor can I get an answer as to whether the glass is curved or flat where the hinge attaches. Maybe you wouldn't mind checking with a straight edge on yours real quick?

 

Sure, i'll be home later today, i'll check.


if Im not mistaken I think it is SLIGHTLY curved ?


Are the hawks one interchangeable with left / right? Or do they specify which side they should be used on?


What I find odd is that these al lbreak a while after installation.

 

1989-pontiac-firebird-firebird-2d-hatchback-white-8.jpg (1100×733) (classiccarsmarks.com)

For now...........Just looking at this one, it appears there is some kind of curvature that flows with the roof.......? Can't tell for sure though..god i want this car lol

 

I took some photos I will also upload to https://www.thirdgen.org/forums/body...-breakage.html

There is definitely a long metal piece that is part of that metal strip that frames the glass. It's far longer than the hinge plate. I do not see a way that when installing the Hawks hinge (flat) it would stress/bend that metal or the glass. My bolts were just barely hand tight so no overtorquing.

 

Did you also use the hawk's nuts / through bolts? (the bolt that goes through the glass)

 

Yes. Sure did. Actually had to cut the old ones off they were frozen. Big pain for the shop.

 

do you think those have anything to do with it?


I can;t imagine though

 

I can't see the thru-glass bolts playing any factor, unless they were really torqued down hard. I see two "pressure points" on the glass....the hinges, and the hatch pull down. The issue would be whether the OEM hinges all had that bow/bend in them (split answers) or if they were flat from the factory. If they had the bow made that way, then the Hawks flat hinge might be a problem. I talked to a company today that makes polycarbonate, but you have to drill out holes and they won't hold up in bright sun. Still, the polycarbonate is flexible so that eliminates the stress explosion issue.

 

this is really a mustery...

can;t wait to get home and see what i find

 

Definitely. Just like the debate over whether the misalignment to hatches was bowed hinges, or the hydraulic lifters pushing the rear deck literally off of the glass. Who knows. I'm just sick over my hatch shattering.

 

I don;t balme you. I'd be sick / i am scared of this too,.....



What I don't get about the decklid part though is, the metal trim around the glass trim is screwed INTO the decklid so securing it into place...if the decklid were pushed out you'd think the screws would be pushed out t/ broken / show symptoms of being pushed out too??

.....so technically ithe decklid shouldn't move / be pushed out since the trim and those screws ar securing it in place with the glass, right? deep thoughts lol

 

I wasn't aware that edge trim was screwed into the back decklid. Yes, if the decklid was pushed back I'd expect to see those screws damaged or gone. But I have that wrap around aero wing and it conceals that.

 

There appears to be SOME kind of curvature for sure

 

I dont know or think its enough to cause an issue though?!?!?!

 

Good question. I wonder if the part of the glass that the hinge plate actually touches (underside) has much curvature. If it does, could that be why some OEM hinges seem to have the bow, essentially two round contact points at each hole in the glass, and a gap between the back of the glass and the hinge plate? E.G. no direct pressure on the glass in between or to the outer sides of the bolt holes?

 

I'm thinking the answer is becoming increasingly clear.
Judging by the pictures posted below and the amount of engineering GM obviously put into the hinges it would seem that the curve in the glass must be compensated for in some way. GM did with the urged hinge and complex padding. Hawks does not. This implies to me that those withbgood experiences with the Hawks have done their own method of compensation.
Does that not make sense?

 

I'm curious about the GM hinges 'bending" . Where / what part actually bends? Like can we get a circled pic or someone pointing to the "bend"?



I have not seen an actual picture of said bending. or at least there are pictures of hinges but im trying to see "the bend".

 

I find it difficult to believe that they become bent.
If you look at the top two pictures in my post above you can see how the hinge is arched between the mounting pads. I'll say that if you were to take an OEM hinge and place on a flat surface, there would be a gap between the bolt holes. Not much of one, but certainly not flat. This would include whatever is integral with the pad itself. I think that the pad is making a difference too.
​​​​​​But I could be wrong.

 

I agree. Someone needs to do a comparison of a GM one to the Hawks side by side.

Im not convinced the GM ones are flat like the hawks (mounting area to the glass)

 

I'm still getting glass cleaned up. I do recall getting one hinge-hatch bolt of the 4 free on the old hinges and swung it around. I did not note any padding/gasket and the bottom appeared pretty flat. Yet, you could definitely see bowing/curvature when in place. I know I made rubber gaskets for the shop to use and I think they may have not. There's another whole thread on exploding hatches (link below) and pics. I also found a set on ebay (doesn't say exactly what year they came from) and that bow is absent. However where I see more of an issue is with a convex glass being compressed onto a flat surface, as opposed to the glass being concave, in which case, the metal would compress against the "top" of the curvature. I don't know at this point. Has anyone contacted Hawks? Chronic Hatch Glass Breakage - Third Generation F-Body Message Boards

 

Could you post comparisons of your old and the hawk's hinges? Like the glass mounting area on a flat surface?

I don;t paln to get Hawk's hinges but would be good to know whats going on!


that other link i provided where the guy was redong his hatch / hinges.....he used Hawk's hinges he said.

 

Unfortunately, I forgot to take "before" pics of the old hinges............