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Welded rear crossmember

Old 11-22-2017, 06:44 AM
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fede
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Default Welded rear crossmember

I found that the rear crossmember is welded to the frame.
Has anyone done it? What are the drawbacks of having it like this?
Old 11-22-2017, 08:43 AM
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doorgunner
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welds eventually crack......running a torch over the weld after it is completed makes it last much longer.
Old 11-22-2017, 10:33 AM
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blue427
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Originally Posted by doorgunner
welds eventually crack......running a torch over the weld after it is completed makes it last much longer.
I don't know if welding the rear crossmember in is a good idea or not,I don't know if that crossmember will fall out or last forever up there,but what you have stated is incorrect.As a certified weldor(or not er as welder is the machine) for 40+ years(certified from .005 of an inch to infinity,in arc tig and mig on aluminum,steel and s/s and pressure and vacuum,range 7(decmal point,6 zeros and 1,.0000001,) FAA certified on landing gear and explosion proof welding(military tanks)plus other"stuff") I'm fairly sure you are incorrect. No disrespect to you.
Old 11-22-2017, 10:58 AM
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Alan 71
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Hi,
If the cross-member is welded in place the only access to the 4 bolts that mount the rear differential case to the cross-member is by cutting a hole in the floor of the rear compartment.
Some folks may not want to do that.
Regards,
Alan
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Old 11-22-2017, 11:39 AM
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fede
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Thanks Alan, that is probably a considerable drawback. Not an issue right now because the frame is off but something to consider if I need to get some work done on the rear end in the future.
Maybe if I get the bolts/nuts welded to the crossmember top too it allows to lower the differential in the future?
Old 11-22-2017, 11:48 AM
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Alan 71
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Hi f,
Typically folks loosen the bolt at each the end of the crossmember and 'drop' the differential and crossmember as a unit…. and then remove the 4 bolts to separate the crossmember from the differential.
Regards,
Alan



Last edited by Alan 71; 11-22-2017 at 05:46 PM.
Old 11-22-2017, 12:31 PM
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On mine with 1350 driveshaft stuff, because the diff is now higher lowering the cars rear, I had to clearance fiberglass for clearance! You might have clearance problems to with 1330 stuff!

Last edited by TCracingCA; 11-22-2017 at 12:32 PM.
Old 11-22-2017, 01:50 PM
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Originally Posted by blue427
I don't know if welding the rear crossmember in is a good idea or not,I don't know if that crossmember will fall out or last forever up there,but what you have stated is incorrect.As a certified weldor(or not er as welder is the machine) for 40+ years(certified from .005 of an inch to infinity,in arc tig and mig on aluminum,steel and s/s and pressure and vacuum,range 7(decmal point,6 zeros and 1,.0000001,) FAA certified on landing gear and explosion proof welding(military tanks)plus other"stuff") I'm fairly sure you are incorrect. No disrespect to you.
But my Industrial Arts Teacher in 1965 said it re-aligns the carbon molecules which prevents weak areas in the (stick) weld.
Old 11-22-2017, 04:15 PM
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ignatz
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Originally Posted by Alan 71
Hi,
If the cross-member is welded in place the only access to the 4 bolts that mount the rear differential case to the cross-member is by cutting a hole in the floor of the rear compartment.
Some folks may not want to do that.
Regards,
Alan
There's another way Alan, you just have to be a little creative.

Originally Posted by ignatz
JayRay: I was very leery about the crossmember bushings being badly stuck on the frame the first time I had to drop the differential and came up with this method, which I have posted before.

..............
An alternative method to get the differential out without removing the crossmember is to use a flat ratcheting wrench and a deep hex socket as shown. See below. This just fits the narrow gap between the body and the crossmember and you do need to be a little adept with your fingers, etc.

Additionally some long bolts with the heads cut off and loosely held serve to reposition it going back in.

Why might you choose this? Well when I pulled the body off I had to pound on my 45 year old crossmember with a sledge to get it out. These things don't just pop out. And of course going back in you'll want new rubber insulators so that is certainly a consideration, as they also are a bitch to get out. And course if you really really want to change out the bushings, installing the aluminum pancakes is a nice upgrade.

The only real downside is you can't correctly torque the mounting bolts. But in 10 years of hard use, it never loosened on me.


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Old 11-22-2017, 06:05 PM
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71 Vert LS1
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I worked for a company that welds many types of metals. If properly prepared the weld is stronger than the metal around it. Never saw any cracks in over 30 years. And who uses a stick welder anymore when working on cars? Hard to tell what bubba has done in the past. Is it possible the cross member tapped bolts holes are stripped out?
Old 11-22-2017, 06:28 PM
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MelWff
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can you provide a picture of this welded rear crossmember just to make sure we are all talking about the same thing?
Old 11-22-2017, 07:17 PM
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Sure but I only have crappy pictures as usual...

Old 11-23-2017, 06:22 AM
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bazza77
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Ah ! so is it the very back one that's now permanent , with the big flat piece of homemade bracing. ?
Old 11-23-2017, 08:32 AM
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Hammerhead Fred
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Originally Posted by fede
Sure but I only have crappy pictures as usual...

If you are referring to the gas tank support as "the last cross member"; once welded in how will you be able to get the gas tank out should that be required after mating the body to the frame?
Old 11-23-2017, 08:39 AM
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No, I was referring to the crossmember, the one that the diff bolts too. The beam that looks like it has 2 cup holders in the middle.

According to my brother that thing is welded to the frame.
Old 11-23-2017, 09:06 AM
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Alan 71
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Hi F,
Typically that cross-member is bolted to the frame with a single bolt at each end.
There's a pocket and a large rubber bushing.
When in place the cross-member could well look like it's welded in place.
Even with the bolts removed often the cross-member won't release. Typically a large 'pry' bar is needed to break the cross-member loose.
Might your cross-member be 'stuck' in place?
Regards,
Alan




Last edited by Alan 71; 11-23-2017 at 09:10 AM.
Old 11-23-2017, 01:44 PM
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MelWff
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can you provide a side view picture identical to the last one in the previous post from Alan 71?

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To Welded rear crossmember

Old 11-23-2017, 02:43 PM
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caskiguy
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Here is a diagram of the cross member assembly.


Hope it helps.
1970 Crossmember



1970 Crossmember

Last edited by caskiguy; 11-24-2017 at 11:31 PM. Reason: Added photos
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Old 11-23-2017, 06:44 PM
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Nowhere Man
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Isn’t that bushing a integral part of the rear suspension. What would be the benefit of welding
Old 11-23-2017, 11:31 PM
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doorgunner
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Ohhhhhhhh,,,,THAT crossmember. Forget everything I said.


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