Engine cradle front cross brace - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 12-29-2009, 12:42 AM   #1
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Default Engine cradle front cross brace

I discovered that a bolt securing the front cross brace to the right frame member was not torqued down. It'* been like that for a long time, perhaps even from the factory. I tried to torque it down, but it is very tight, either because of corrosion in the threads or the wrong bolt used.

Does anyone know what the proper thread is for this bolt so I can tap the threads to clean them out? I see that there is at least one other bolt holding this cross brace, so it is probably not critical. But I want to secure this bolt in the near future.
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Old 01-01-2010, 01:40 PM   #2
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I have since found that the wrong bolt had been installed. It seems that the previous owner had some work done that involved removing that brace. The correct bolt is a 3/8" 20 threads/inch bolt. Does anyone know the proper torque for this bolt? Should it be a compression thread? I have it torqued to about 50 ft.lbs right now with a lock washer. But with the normal twisting and vibration I will expect this bolt to work loose.
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Old 01-01-2010, 02:35 PM   #3
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My 2000 FSM says 141 ft lbs. You can call the dealer and see if you can find anyone that can give you specific info for your ride. Definitely, 50 ft.lbs is not enough.
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Old 01-01-2010, 03:33 PM   #4
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Thanks. I knew that 50 ft.lbs would not be enough, but if I overtorqued it and stripped the threads I'd really be messed up. Also, I'll have to get a proper bolt that can take that torque. I'm not sure if the one I used is rated for 150.
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Old 01-01-2010, 06:37 PM   #5
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Quote:
Originally Posted by enslow View Post
Thanks. I knew that 50 ft.lbs would not be enough, but if I overtorqued it and stripped the threads I'd really be messed up. Also, I'll have to get a proper bolt that can take that torque. I'm not sure if the one I used is rated for 150.
This is pretty good info and may help you. You are correct that the right bolt and nut needs to be installed to handle the torque. The threads don't get stripped during the torque, but a stud can stretch and fracture if its under rated for the torque.
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Old 01-01-2010, 10:33 PM   #6
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Are you speaking of the bolt with nut in the front right corner that holds the subframe pieces together? If so, the bolt you found it close.. probably should be an M8 1.25 or M10 1.50 thread. 98%ish of the bolts on our cars are metric, most of the non-metric are part of the engine assembly.

Sorry..can't find a torque on that. I would say 75-100 ft lbs would be in the proper range.
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Old 01-02-2010, 03:16 PM   #7
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I found a picture showing the bolt in question, thanks to Danthurs' ACC belt thread. The bolt that fits now is 3/8" with about 20 threads/inch. However, it seems I should probably find a metric replacement. Maybe I'll drop by a stealership and see if they have one on hand.

The only problem is I'm not sure how to upload images from my computer. I seem to be only able to upload images from the net.
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Engine cradle front cross brace-bolt-image.jpg  

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Old 01-02-2010, 08:29 PM   #8
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I checked with the dealership and they told me that if I got the bolt tightened to 50 ft.lbs that'* plenty. There is no need for me to do anything further.
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Old 01-03-2010, 01:16 PM   #9
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Yes, that is one of the couple I was thinking about. There are three up there that hold that part of the cradle together. And three by the driverside rear corner of the subframe as well. That'* where it comes apart to allow the trans to slide out the bottom w/o taking the whole subframe down.
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