I bought a frame from a 65 chevy truck to use the rear truck arms on my 53 chevy car after I removed the trailing arms I noticed there is a little rust starting in between the 2 C channels and I was wondering if I can drill out the rivets sandblast and paint then just bolt the two C channels back together. I was thinking some 7/16 grade 8 fine thread bolts but I know these arms are designed to flex and I just worry about the metal egging out or the bolts breaking. Anyone ever do this?
Haven't done it, but see no problem with what you propose. 7/16" bolts sound a little big to replace the average size spot weld........except at the rear of the arms where the u-bolts pass through. For the rest of the beam I would think 5/16" would be adequate. Also, depending on the size of the drilled out spot welds, after cleaning them you could just weld up the holes or you could drill a new hole in one beam half adjacent to a removed spot weld, and rosette weld that spot. A good self etching primer on the adjoining surfaces, folowed by a good paint coating after assembly, should resist rust for a long time. Ray
460 Willy, Depending on how badly your swing arms are rusted, that repair may work. I had to replace one a few years ago & after a few trips thru the salvage yards, I found a good replacement. Classic Industries & several others sell replacement arms (this is not meant as an endorsement of one vendor over another but LMC prices are generally higher) A few other also sell a reinforcement plate set that welds to the top & bottom of each swing arm. I'll repost a link as soon as I can find one. Lowered springs, longer panhard rods, & poly bushings are also available for this rear, possibly the best ever made (IMHO).
460Willy ... here's my version ....about a month ago I finished my trailing arms for my '65 C-10. My resto job consisted of sandblasting and mig-welding the arms "water tight" Wedged open the halves and sandblasted in between up to the front pivot before clamping and stitch welding, a coating of zinc primer was sprayed in between the channels The rust flakes around the spot welds pulled a bulge that had to be hammered out Ground a depression and plug welded every former spot weld, even the those 5/8" holes were filled Creative clamping, the U-bolt holes were resized with a 3/4" barrel drift pin All done... the only weird thing was the mig gun cone accumulated a lot more spatter from this job...maybe from the zinc metal primer?
While keeping water out of the joint is desirable, I think welding the entire length of the arms is way overkill and may even have some downside. These things are intended to 'twist' along their length as the suspension responds to body roll in turns. That is one reason why they are "I" beam style beams. An alternative method to consider, after spot welding, would be to use a good professional quality seam sealer that body shops routinely use. It is absolutely paintable and remains flexible even after fully curing. Lastly, because good used arms are getting pretty scarce, I chose to buy some from Stock Car Products. They are not cheap, by HAMB standards, but they are very well made in the style of the originals and the front bushing end can be fitted with either a rubber bushing or a "Johhny ball" (spherical ball). Several aftermarket suppliers for this period of GM trucks market kits that use square tube for their versions and that is totally incorrect as the square tube DOES NOT allow the longitudinal flex required by the original application of the design. There seems to be a common misconception about the forces at work when trailing arms are rigidly mounted at the axle end as opposed to what forces are applicable when they are bushing mounted at both ends. Therefore, I strongly discourage using the square tube aftermarket units or home built copies of same when rigidly mounted. If one is going to home build these puppies, incorporate the "I" style for satisfactory results. Ray
About 15 years ago a friend was restoring his '65 C-10. He removed the arms, separated the halves by drilling the spot welds, and sand blasted them. Then he had them powdercoated separately. He put them back together with 7/16" fine thread Grade 8 hardware, installed new bushings/u-bolts etc and the truck has been on the road ever since. This is a big block powered truck that pulls mid 12's at the track and gets driven on the rough city streets regularly. A lady backed into the bed of his truck a few months ago, so when he pulled the bed off for the repairs, we took a good look at the arms and suspension...they still look new. I'd say the bolting of the arms has held up just as good as the spot welds, and powdercoating the halves separately will help prevent them from rusting for many years to come.
Thanks guys I am glad to hear that I am not the only one who has decided seperate the halves and try to preserve them. The rust doesn't seem really bad but I will not really know until I sand blast them.
Here is a link to the re-enforcing plates. You get 2 top plates, 2 bottom plates, plus new poly bushings & new U bolts. http://www.classicperform.com/Store/1960_1972_Chevy_Truck/6072TARK.htm
I'd like to see someone document this claim that the arms twist. No confirmation, but I believe the arms were designed to be able to twist without breaking their bolts, brackets, etc. but that in normal use they do not twist through the normal range of suspension travel. I agree that continuous welding top and bottom is unnecessary, it's probably not damaging; the 3/4-ton arms had reinforcing plates on them.
I really doubt also that the arms twist. Too many others things that would give before the arms would twist. My opinion.
I'm pretty sure the front bushings in the truckarms can accommodate more lateral and rotational movement at the rear of the arm than the arms ever see when bolted up to an axle.
This is a perfect example of the minimal amount of knowledge aftermaket mfgs have. Look at the basic design of this rear suspension, the arms have to be able to twist, how many stock arms that haven't rusted have you ever seen fail? Aftermarket tube arms rip apart the crossmember and axle mounts all the time. Who spent more money on design G.M or an aftermarket company. A junkyard is your best friend, not some junk peddlers catalog!
The factory probably built them as an I beam unit because it was cheaper to stamp them out. If they do flex, the rubbing will wear off paint or powder coat. Some of the old riveted bridge beams that we cut in a shear had tar between the plates that was still flexible.
Yes, they do have to be able to twist, but welding them or plating them is not going to prevent this.
Why? The rubber Silenbloc bushing at the front of the arm allows probably 25-30 degrees twist of the arm (12-15 degrees either side of vertical) and about the same in lateral movement at the end of the arm. The arm is stiffer than the bushing and isn't going to flex until the bushing shell bottoms out. Under what conditions would a truckarm suspension in an on-road vehicle reach that limit? Certainly if you do it's preferable to have the arm flex rather than break, or break the bolt and/or the bracketry, and I'm inclined to believe GM took this into account. But I'd think if the arms were seeing that much twist they'd chew up and spit out bushings right and left and to my knowledge that doesn't happen. The arm does not move in a flat arc in any case, which is why you have to have a flexible bushing there. I suppose a spherical bearing or something like a Johnny Joint would work but to my knowledge even race classes that run truckarms use Silenbloc-type bushings. I've got a friend who's a crewchief on a Sprint Cup team, I'll have to see what he's willing to tell me.
All you have to look at is the basic design of this system, solid rear mounting, 2 front mounts, now just make a right turn into a steep driveway, this is the what Chevrolet built this suspension to do, If your going to drive on a smooth race track, with next to no suspension travel,weld your axle to the frame.
I split mine, to clean and then welded them. I agree with JEM, they don't need to twist - thats what the rubber bushing is for. I designed the rear suspension on my avatar, modeled it after chevy truck design. There is no twist in my arms, they attach at the front with a heim joint which allows the twist - just like the rubber bushing does in the stock suspension.
..and as the right wheel goes up the arm pivots upward in a curved arc, twists slightly and both the twist and the side-to-side motion of the rear end of the arm relative to the axis of the front pivot would be accommodated by the rubber bushing in the front of the arm. Why would the arm itself need to twist and given the stiffness of the arm how could it do so without destroying the bushing?
They twist. In normal driving conditions they do not need to twist alot, but it doesn't take much comprehension of the forces at work to understand they need to twist some when the axle housing rotates along the axis of the driveshaft in relation ot the chassis (think body roll when cornering). I am not saying that the halves of the control arm twist in relation to one another, only that they flex as a unit. And that such flexing is essential to the axle/chassis movement. Without such flex, excessive strain is placed on the axle housing/control arm juncture and/or the control arm itself. Ray
Since this 6 year old thread was brought back up, I'll add my 2 cents The twist is the reason that NASCAR Mandates that the arms be I Beams!
Hello Sir, I would suggest you check the hot hemi heads section that deals with parts and motors etc for all things hemi.
Only when the information won't be of use. Like an old thread about something that was time sensitive to get a car running, sold, or a part for it. LOL - Just my warped thoughts. Or worse yet a 10 year old thread and the newbie's response is "Dude, that sucks" And your response was both informative and appropriate
The 3/4 and 1 ton units have extra plating riveted to the arms. These arms also make very good traction bars mounted in line with the leaf springs. One last question Does the truck called the Farm Truck on the TV show still have the long arms?? That thing does launch hard. Thank You.. Bobby
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