had a weird noise coming from the drive line so I crawled under the car and my torque tube is cracked. I just replaced my clutch and trans now this. What a bummer. When I first put the car together it would sometimes bottom out. Could this have been the start of this crack? Anyone ever have this happen?
What, and where was the car bottoming out? On the rear, or the torque tube? What are you running for motor. transmission?
Rear was bottoming out, could have been at the cross member too. Raised the car a few inches and no more bumps. Car has a 59 ab and 39 box. Torque tube is a 28 hooked to a 38 rear end with 46 radius rods.
Never seen anything like that,possibly the torque tube has had a hairline crack for years and it finally gave up. HRP
How is the suspension set up? Looks like the torsion bar( wishbone) mounts right at the break?If the suspension doesn't have enough travel, bottoming out could possibly cause this as a side effect. As someone else said, never seen that happen before. Good luck with it. Mike from Mass.
looks like you have a stress crack in front of the pivot mount, which looks welded to the tube. looks like a simple stress crack from age that started in the heat affected zone.
Damn that sucks. I might have a guy who can weld that if you want to go that route. I'm not sure if it would hold up or not but he specializes in welding old oil soaked metals, apparently he's got a system down.
I also think the break is related to the weld; probably caused by weakening of the metal that crystallized. This might not have happened without bending stresses from bottoming out. Shit happens. Find fresh metal, because the weld in your picture, more than likely, was done with an arc welder in one pass, and it made a lot of heat. To duplicate your part, have it welded by someone who knows about heat cycles, and uses a tig. Others may disagree.
I welded the pivot on with a mig letting it cool between passes. I have other tubes Kickin around, I will most likely use a later tube this time and tig the pivot on.
As the old HAMB metallurgist, I think your radius rod mount is the likely root cause of the problem. The stress concentration at the front of the mount initiated a fatigue crack, which then propagated. An easy fix is to clean the crack, grind with some V groove, and then weld it back together. You should put a reinforcement plate where the radius rod mount is located so it reduces the localized stress at that point. With that it should be good for many more years. BTW, metal does not get weaker with age, or crystallize. Those statements are just incorrect. Fatigue of metal is a cracking that occurs at below yield stress levels, due to cyclic loading. It is not because the metal loses strength over time. Metals are always crystalline, that is their structure all the time. Different crystal structure depending on cooling rates and heat treatments, but they are always crystalline structure. Welding does create problems and you can get different mechanical properties in the heat affected zone, the area just near to the weld. This is especially a factor when the part is heat treated or has specific actions such as cold working to make stronger. The heat from the welding destroys the hardening or special treatment. Essentially any welding reduces the mechanical properties down tot he lowest level annealed or normalized level. However for onekoolkat1950, I believe the problem is due to stress concentration more than due to the heat affects from the welding. The torque tube is not a heat treated part, and in fact is a welded part as originally manufactured.
Thank you 38 chevy that was very informative. How do you propose I add strength to the mount area? Thanks- Ray
My uncle used to warn me about "Hydrogen brilltization". He said this occurred when welding old steel such as a frame and would weaken the material. What are your thoughts?
I add strength to the mount area?, I think you said you will use another tube, right? I would just weld a plate in the area that the arm mount will be installed. that being said I would not weld a pipe all the way around the torque tube at this area.....that would be a crack just waiting to happen.
38chevy454, I like the way you talk! one of the best metallurgy posts I've read on this forum. I will add that there is not all that much stress at the point of failure, so the crack is most likely caused by damage rather than fatigue. (bottoming out or hitting a rock with one rear wheel) It is 70 years old, God knows what or when.
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