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Loose subframe bolts

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Old Mar 14, 2017 | 10:49 AM
  #1  
Tootie Pang's Avatar
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From: Los Angeles
Car: 1989 IROC Convertible
Engine: 350 TPI L98
Transmission: WC T5
Axle/Gears: 3.42
Loose subframe bolts

I'm not sure who did what to the car I just bought, but most of the front body panel bolts were lose so I tightened them up.

Last night, doing motor mounts, struts, etc, I notice one of the big carrier(?) to subframe bolts was loose. The one just above the rear lower control arm pivot bolt. I torqued it to about 100 lb-ft but couldn't find a torque spec.

I checked others, they seemed fine.

Is this typical for these cars or perhaps someone was careless with some refitment?
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Old Mar 14, 2017 | 01:17 PM
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From: N.E. Ohio
Car: 87 Gta
Engine: 5.3
Transmission: 4l60e
Axle/Gears: 3.42
Re: Loose subframe bolts

Originally Posted by Tootie Pang
I'm not sure who did what to the car I just bought, but most of the front body panel bolts were lose so I tightened them up.

Last night, doing motor mounts, struts, etc, I notice one of the big carrier(?) to subframe bolts was loose. The one just above the rear lower control arm pivot bolt. I torqued it to about 100 lb-ft but couldn't find a torque spec.

I checked others, they seemed fine.

Is this typical for these cars or perhaps someone was careless with some refitment?
Hard to say. Iv changed some subframes in newer cars and have seen bolts missing! Maybe a defect from the factory or someone else has been into the car? With the age I'd go with someone being careless.
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Old Mar 14, 2017 | 02:10 PM
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From: Chasing Electrons
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Re: Loose subframe bolts

They are k-member bolts, our cars don't have a sub-frame. Here are some links to short threads with good info on the location of and the torque spec of those bolts:

https://www.thirdgen.org/forums/susp...passenger.html
https://www.thirdgen.org/forums/susp...-k-member.html
https://www.thirdgen.org/forums/susp...our-front.html


RBob.
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Old Mar 14, 2017 | 04:30 PM
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From: Los Angeles
Car: 1989 IROC Convertible
Engine: 350 TPI L98
Transmission: WC T5
Axle/Gears: 3.42
Re: Loose subframe bolts

Thanks, I noticed many commented that the third post should be a sticky. I agree!



Last edited by Tootie Pang; Mar 14, 2017 at 04:40 PM.
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Old Mar 14, 2017 | 07:50 PM
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Car: '89 Firebird
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Transmission: T56
Re: Loose subframe bolts

Where did that graphic come from? 160 N-m is standard torque for a 14 mm bolt.

The K-member bolts on my '89 are M12 and a bolt of that size has a standard torque of 100 N-m, and a high torque of 105 N-m for structural members. Coincidentally (or not so coincidentally), the GM service manual for an '88 Firebird (the only version I can find) calls for 105 N-m torque.
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Old Mar 14, 2017 | 08:42 PM
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Car: 1989 IROC Convertible
Engine: 350 TPI L98
Transmission: WC T5
Axle/Gears: 3.42
Re: Loose subframe bolts

89 Service Manual
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Old Mar 14, 2017 | 08:55 PM
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Re: Loose subframe bolts

I'd pull a bolt and measure the thread size. If it is an M12 then throw all of them in the trash and buy new bolts, and then torque it properly.
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