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Discussion Starter #1 (Edited by Moderator)
Body Bushing Replacement GM "A" Body







Although our beloved GM Intermediate ("A" bodies:Chevelle/Malibu/El Camino, Tempest/GTO, Cutlass/F-85, Skylark, Sprint, andsimilar) are known to have "Full Frame" construction, you might be surprised towitness how flexible the frame actually is. One source claims the frame wasdesigned to flex in order to "improve" the ride quality. The body, while not as rigid as a "unibody", is surprisingly strong. All those stampedsheetmetal panels welded together as a 3-D assembly provide considerablestiffness. The body needs to be properlyattached to the frame so the strength of the body can be combined with thestrength of the frame.

Attaching the body to the frame is accomplished at thefactory with multiple rubber cushions and steel hardware; the rubber isolatesvibration and noise, yet the rubber-under compression from the attaching bolts'n' washers-allows the body structure and the frame to work together to resistflex. The number of cushions varies withthe year and the model; convertibles generally have more cushions thannon-convertibles.

My particular El Camino was an incredible rattle-trap. Every bump in the road produced squeaks andgroans. If I tried to jack up the truck,I could watch the body and frame separate because the rubber mounts through theradiator support were completely rotted out, as were the mounts by the tailgate. Because the radiator support was no longerproperly attached to the frame, and the front of the fenders hang off of theradiator support, the front fenders no longer aligned with the rest of thebody. In fact the driver's door caught on the back edge of the front fender,producing a wonderful crease in the door, and the most amazing oil-can PA-PING!every time the door opened.

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The obvious solution was for me to replace the body mountcushions before re-aligning the fenders and doors. I purchased a set of polyurethane bodymounts, and then waited about five years to work up the courage to actually performthe service. I had every expectationthat the job of replacing body mounts would be a hateful procedure, filled withexplorations into new ways of cursing 'n' swearing. In the meantime, the'Camino sat in the back yard. Itwas too ugly, rusty, and creaky to take any pride in, and I probably didn't put100 miles on the thing in those 5 years.We had an agreement, the El Camino and I: I ignored it, and it continuedto rust. You see, installingthe mounts is-usually--no big deal. The realproblem is getting the old mounts out. There are three different things that canhappen when you try to remove the old rubber mounting cushions:

lThe old bolt unscrews from the nut andeverything is happy. If ALL your boltsunscrew, go buy a lottery ticket! You'reonly gonna need one; today is your lucky day.

lThe old bolt is seized in the nut; and yourimpact gun turns the bolt hard enough that the nut distorts its cage and justspins-or the cage tears its spot-welds.Either way, the cage no longer prevents the nut from turning. You may have to cut open the body to removethe cage, and hold the nut with a wrench while you continue to rattle the boltfrom underneath with Mister Impact Wrench.Then, with the bolt removed, you clean up the nut and re-weld the cageto the body.

lThe old bolt is seized in the nut; and the boltshank is so corroded that the bolt breaks leaving a perfectly good cage stillwelded to the body. You may have to cutopen the body to break the spot-welds on the cage, and then pull the nut-and-broken-boltout from the top side. Then, with the bolt removed, you clean up the nut andre-weld the cage to the body.

On my 'Camino, there were ten body mount bolts. There are fourteen cushions, but fourcushions were not secured with bolts-they're just sandwiched between body andframe. Five bolts came out, three spunthe nuts, and two bolts (which started out with 7/16" shanks) were rusted downto about 1/4" diameter; the shanks twisted and broke.

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As it turns out, ifyou remove the front inner fenders, you can access the two nuts at the firewallthrough existing openings in the body.(Four nuts on a convertible, I guess-two on each side because theconvertibles have double cushions at the firewall.) Those nuts did not have cages on them whichis why they just spun when I tried to unscrew those bolts. Apparently, GM expects you to pull the innerfenders for access, and so welded cages to trap the nuts in place aren'tprovided. One inner fender came outquite nicely; the other had it's own seized hardwareand about half the bolt heads had to be blown off with an oxy-acetelyne torch. Ire-installed the inner fenders with new bolts and extruded nuts, andanti-seize.

The other three "problem children" required the body to becut open to access the nuts 'n' cages. Icut the body with a die grinder and abrasive cutoff wheel. Clearly, you want eye, lung, and earprotection, it's loud; and the abrasive wheel dust and steel sparks arenasty. Never stand in-line with anabrasive wheel, they can and do explode (!!!) with little warning particularlyin the hands of someone who doesn't have a lot of experience with cutting a straight[/B] line. Some cutoff tools come with a clear plasticshield. I won't say I like that kind-theplastic doesn't stay clear very long, and then you can't see what you'recutting. OSHA won't approve ofnon-shielded cutoff wheels, though.You'll want to be sure that you're cutting in the right place, directlyover the cage nut and with enough room on each side of the nut for toolclearance. As far as I'm concerned, it'sbetter to cut a bigger access hole intentionally than to have to cut-andre-cut-and re-cut because you didn't cut in the right place the first time.

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Removing the cages is best done with a spot-weld cutter-buta ~1/2" drill bit will work. Figure outwhere the thing was spot-welded (two spots per cage, one on each flange) anddrill the spot welds in the cage but avoid drilling the body. Then knock the cage free from the body with ahammer and chisel, or an air hammer 'n' chisel bit by trying to pry between thecage and the body. It can take somewire-brushing and close inspection to figure out where the spot weldsare-depending on how much rust is covering the cage.

As it turned out, my 'Camino had been hit in the front endat some point prior to me buying the thing.I knew this, and I believed the damaged had been localized to the veryfront of the right side frame member-where the bumper brackets attach. In reality, the frame from about the firewallforward had been tweaked-and then improperly pulled back. The radiator support and bumper brackets weremore-or-less in proper position.Unfortunately, the frame was still tweaked at the firewall bodymount. This also explains why theoriginal body mount in this position was ripped. The frame surface that the cushion sits onhad a small mountain in it that pushed into the rubber and overstressedit. I bashed the offending peak with ahammer until it submitted. Since theframe was cracked right at the peak, each side of the "mountain" tapped downfairly flat. Then I welded the split inthe frame, and shoved a new cushion back in. It took power tools, big pry-barsand a lot of harsh language to get the bolt through the hole in the body. Yes, I realize that the frame should be professionallypulled into position, and no, that's not going to happen anytime soon.

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I knew that the radiator support brackets were rusted; I'vebeen looking for a replacement radiator support for quite a while. Most of the ones I've seen are just as bad asthe one I have; the battery acid leaks onto the rad support and corrodes therad support and the inner fender. I cansave the inner fender, and I've found a usable rad support, for futureinstallation. For awhile, though, thisis what I'm stuck with.

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Now, let's be clear. Installingnew body mounts is actually a pretty easy job most of the time. I lifted one side of the body off the framean inch or two, using a floor jack and a 4-by-4 up against the pinch-weld tospread the stress, being careful to support the body so it won't drop and crushmy fingers. I'd thought about what itemsare frame-mounted; and what items are body-mounted-and tried to keep in mindwhat's going to happen when the body is jacked up off the frame. Some potential issues:

lAssure the fan shroud (mounted to the body)isn't being lifted up into the engine fan

lAssure the metal brake tubes from brake mastercylinder to frame; and the brake hose at the rear axle aren't beingover-stressed.

lAssure that the steering column isn'tover-stressed

lVerify that the various wires that are routedbetween body and chassis aren't being pulled.

lAssure the clutch and shift linkage from body toframe isn't overstressed.

lVerify distributor-to-firewall clearance.

Take out all the old cushions on the side that's lifted,chase the threads in the nuts with a used tap or re-threading tool. The instructions included with the new Polymounts says to re-use the flat washers and the washers with the sleeves. All my old hardware was rusted to death; andI couldn't find a supplier for the stamped washer/sleeves. I fabricated new sleeves from steel tubing,(four @ 3/4" OD and six @ 1" OD-but your requirements may vary) and just used anew flat washer top and bottom. Usethin- or thick-wall tubing-your choice.

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Stuff the new cushions in place so the shoulders pokethrough the holes in the frame or the radiator support brackets, and set thebody back down. I used a tapered punchor a tapered pry-bar through the center of the mounts to assure the mounts arein line with the nuts since the bolts I used didn't have the tapered section atthe top like the original bolts. Iapplied anti-seize to the threads of the new bolts. (I almost never install bolts "dry"-threadedfasteners that aren't anti-seized or lubed are chemically thread-locked, orcoated with some kind of sealant depending on the application. That's a philosophy I suggest you adopt.) Loosely install the new bolts through the newmounts along with the second part of the cushion. Then do the same thing on the otherside. When all the bolts are through allthe new cushions, measure the body-to-frame side-to-side and adjust as neededso the body is squarely in place and centered on the frame front and rear. Torque all the body mount bolts to ~30ft-lbs. The actual GM torquespecification allows up to 45 ft/lbs for my vehicle; but since the bolts arelubricated with anti-seize, I knock off ~20% from the torque spec. Check and adjust door and fender alignment asneeded-I added washers between the frame and the cushion to lift the front ofthe fenders. Testdrive the car, (some bumpy roads preferred) and re-check the torque onthe bolts. They should still have at least20 ft-lbs residual torque.

One unexpected positive result was that I discovered anun-used cage nut already in position in the body under each of the doors. Normally, an unsecured (no bolt through themiddle) cushion goes in each place, but I managed to install a pair oftwo-piece "secured" mounts, torqued with washers and bolts through the "bonus"cage nuts.

Overall, this is a VERY worthwhile-but frustrating-project. I could tell the body/frame was more rigidbefore I even got the vehicle down off the jack stands. Getting fresh mounts and hardware in placeand properly torqued made a H-U-G-Edifference! That said, I've had tore-align the front fenders so the doors will open-even my passenger door wasrubbing the back edge of the front fenders after the radiator support wasproperly secured to the frame instead of floating freely on rotted-out mounts.

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Interestingly, the bushing kit I bought (Energy Suspension3.4115G listed for Chevelle/Malibu '68-72) included everything the 3.4113G (ElCamino '68-72) has, plus a few extra bushings AND it was priced less[/B] at

Summit. Go figure!That's why I had extra "secured" bushings to install in place of two ofthe unsecured bushings specified.

Time to completion given ready access to air tools, welder,cutting torch, etc.:

Best case-all the bolts unscrew readily; you canre-use at least some of your hardware, and you don't have to spend too muchtime re-aligning the fenders: myestimate--Two hours.[/B] Less if you're lucky. Don't gloat.Everyone hates a sore winner.

What I expect to be "typical" time-you're going tocut the body in a couple of places, and the fenders need minimalre-alignment: my estimate--Eight to twelve hours.[/B]

What I spent on MY vehicle, probably close to aworst-case scenario: Eleven hours[/B] to remove all bolts, cutand re-weld cage nuts, and cut and re-weld 3 body openings. All but one boltre-installed. Two additional hours[/B] to remove and replace inner fenders (oneneeded the bolts torched out.) Two additional hours[/B] to rework frame atfirewall cushion and install the last bolt.Threeadditional hours[/B] to align front fenders. Two additional hours[/B] driving all over creation looking for suitablehardware, and fabricating tubular spacers. These times are very approximate; I was toobusy being angry to watch the clock closely.

Parts List not including ordinary shop supplies:



Item



Source



Part Number



Quantity



Price



(approx, as of 10/2008)



Body mount kit



Energy Suspension



Made in

USA



3.4115



(verify for YOUR application)



1



$70



Body mount washers



Fastenall



Made in

China; very weak! I wouldn't have used them If I could have found something else.



11103746



"Extra Hvy Fender Washer"



½ X 2 X1/8



25



(I re-used a few of the old washers)



$50



Body mount bolts



Fastenall



Taiwan



7/16-14 X 2.5"



Grade 8



10 bolts



$12



Radiator support nuts/bolts



Ace Hardware



Made in ???



7/16-14 X 3"



Grade 8



2 bolts



2 nuts



$4



Inner fender bolts 5/16



NAPA



Taiwan



665-1981



7 per package



3 packages



$15



Lower fender bolts 3/8



NAPA



USA



665-2292



4 per package



1 package



$5



Inner fender cage nuts



5/16 short



NAPA



USA



665-1461



7 per package



3 packages



$15



Lower fender cage nuts 3/8 short



NAPA



USA



665-1959



4 per package



1 package



$5



Steel tubing-1" OD and ¾" OD



Local steel supplier; cut to fit.



Thin- or thick-wall



As required



$8

 
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