Body to Frame Bushing Instal Guidance - Pontiac GTO Forum
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post #1 of 7 (permalink) Old 05-27-2017, 08:43 AM Thread Starter
 
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Body to Frame Bushing Instal Guidance

Hey folks, I've tied into a project that seemed simple yet turns out not so much. While resolving a small rust area behind the rear wheels of my 67 Sports Coupe GTO I decided since I was replacing both frame to body support brackets might as well replace them all. With 10 of 12 bolts removed I've had two casualties (broken bolts) those being the mid body bolts. I'll figure those out hopefully without having to cut any metal besides the old bolts.

My question to the group is how much loosening and removing is really necessary beyond the obvious brake lines, clutch linkage, cooling fan, and grounding straps. Does the manual steering column have the flex to tolerate a 3-4" rise of the body. What is the best process to lift the body? I have a two post lift and was planning to use 6 jack-stands to support the body as I lower the frame the needed inches. I have used a floor jack and wood to raise the rear of the body to replace the rear support braces and could easily replace half the mounts by raising the rear. There doesn't seem to be a good lifting spot for the front four mounts.

Looking for experienced owners or mechanics to guide me through the last stage here.


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post #2 of 7 (permalink) Old 05-27-2017, 05:48 PM
 
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Garage
I have not done this this way as I pulled the body off my frame in doing my frame up rebuild, but this is how I might do it.

You don't want to lift the body up 3-4". You will probably damage sheet metal at best. Loosen all the frame bolts so you have a little play under them. Then remove all the bolts on the side you plan on replacing the bushings. Put a long 2 x 4 under the rocker panel and raise it up just enough to sneak out the old bushings and install the new. From what I have read, the hard part may be getting to the nuts that hold the bolts on the firewall bushings as the inner fender may be in the way.

Reinstall the bolts on the replaced side, but leave them loose so they have a little play. Then do the other side. Install the bolts. The look at your body lines to make sure the body has not shifted. If it has, then adjust the body to get your body line squared up again. I would take pics of all the body lines so as to use them as reference and duplicate them if the body shifts on the frame.

So survey the car up on the lift and see if this might work for you.

The broken bolts will most likely not be an easy fix. You will have to get at them through the top, ie the floor pan & under the carpet. You will have to cut an opening/window to see them. The bolts are typically held in by a cage nut that is welded in. You will then have to cut out the metal/cage nut to remove it and the broken bolt. Then cut a piece of new metal to be welded back in with the hole for your bolt to go through. Then weld a new cage nut on to that piece, and then weld your hole up in the floor.

Although this is a '68 Chevelle, it may give you an idea of what I am talking about. Body Bushing Replacement - Chevelle Tech Study your situation and see if the above fix will work. You may come up with a better idea, but this seems to be the typical fix/repair when these bolts either snap or the cage nut spins loose.
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post #3 of 7 (permalink) Old 05-31-2017, 07:18 AM Thread Starter
 
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Thanks Pontiac Jim. I essentially did this on the passenger side using two jacks on my lift arms. Raised it enough to get the mid body top bushing out to work on the busted bolt. I'm trying to avoid cutting a access slot in my perfect floor pan. Tried arc welding a nut to the end of the broken bolt. I guess corrosion has electrically isolated the bolt as it would t spark. I let it go then as I needed to get the wheel wells finished. I should get back to the bushings next week.




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post #4 of 7 (permalink) Old 05-31-2017, 09:12 AM
 
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Have lifted literally hundreds of GM A-body's off their frames. One thing I learned many years ago, using my impact, I just snap waaay too many body bolts. Thats usually no big deal on a parts car I'm cutting up for sheetmetal, but a real pain on a body that is coming off for a frame-off restoration (we only do frame-off's here).

By using a 2 foot long handle flex head 1/2" drive ratchet, with a short extension, and a 6 point 5/8" socket, one can actually feel a body bolt budge as it attempts to loosen. Can also typically tell if the bolt is frozen bad. The only body bolts that I occasionally break are the ones that mount through the frame near the seat belt retractor. One can actually drill a small (3/32") hole through the floor pan into the small pocket that holds the caged nut in that position cage & then spray through the thin tube some Kroil or PB Blaster into the caged nut.

The other trouble spot can be the caged nut that holds the next to the last of the rear body bolts, this is in the front of the trunk floor. The rear corner bolts can't remember one of those that has ever seized. Front body bolts at the base of the cowl, often the cage is broken on them. Can either fight with pry bars to hold the big nut still, or can pull the inner fender, & make a tool to fit down through the window into the body holding the nut. Last thing to note, at least on '68-72's there are 3 different lengths of factory body bolts. Always best to reinsert good condition long body bolts back in their correct position, as putting them in the short positions (trunk) can dimple the trunk pan up.
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post #5 of 7 (permalink) Old 06-10-2017, 05:48 PM
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Good advise here. I concur that if you are replacing the bushings with the car together, the method Jim states will work just fine. You can pry up just enough to slide out the old bushing and slide the new one in. No need to disconnect everything to raise the body way off the frame. I sure like PH's idea of drilling a small hole so you can soak the cage nut and bolt in penetrating oil.....sure a lot less work than cutting a floorpan and welding in new hardware. Go easy on the ratchet/breaker bar, and go in back and forth motions to ease the bolt out. You'll know if it's about to snap...you can feel it 'spring' a bit. That's when it's time to lay off and give it more oil, and time for it to soak in. Good luck.
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post #6 of 7 (permalink) Old 08-04-2017, 08:37 AM Thread Starter
 
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Update on my bushing replacement. All bushings replaced using the 2x4 under the Rocker panels. Worked like a champ with no changes visible on any of my gaps. Trailered the car to Illinois for the Nationals (won Bronze in the Concourse Restored class). After the nationals I drove the car to a local show. On the return drive every time I hit a bump the front knuckles of my driveshaft scrubs the top of the tunnel. What's the probability that this problem is related to my new bushings?


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post #7 of 7 (permalink) Old 08-07-2017, 04:46 PM
 
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It was not much fun when I did mine. Some twisted off in the area between the threads and the head of the bolt. That area seemed to shrink in diameter. I spent some time just cleaning the frame part and painting that area before I mounted the bushings.
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