X-member Necessary?

Greetings,

On my 73, I have a welded in 6 point roll bar. The rear 4 legs are welded to the frame on the kick-ups & near the shock mount. I have also boxed in the area where the differential X-member (sombrero) mounts/ bolts to. So with this, I am wondering if the welded X-member behind this is redundant. In the interest of weight loss, it appears that the X-member could be cut-off after the sombrero mounts and capped. Probably not much gained, but it would be zero cost. Thoughts?

Too many mods to list, frame, body, drivetrain.
383, 4 sp. muncie, 4:11 rear.
backyard build... location: lansing, mich.

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Except for location - that could be my sig!

Picture would help. Here is how I did the rear section - built a sub-frame,: boxed the diff - but kept the x-member as a support for fuel cell and rear body. Guess I could have cut it out and used some lighter material:


Cheers - Jim

73c34me said:

Greetings,

On my 73, I have a welded in 6 point roll bar. The rear 4 legs are welded to the frame on the kick-ups & near the shock mount. I have also boxed in the area where the differential X-member (sombrero) mounts/ bolts to. So with this, I am wondering if the welded X-member behind this is redundant. In the interest of weight loss, it appears that the X-member could be cut-off after the sombrero mounts and capped. Probably not much gained, but it would be zero cost. Thoughts?

Click to expand...

there is no pic but on my car below we got rid of both cross members and made one out of square tubing, raised in the car 1", you will be shocked how heavy that welded in cross member is

Phantom Jock, I see in your pic you have inboard rear rotors. Have you run your car yet with the brake setup? If so do you have a brake heating problem? Any pics on how you mounted the rotors and calipers?

Cole Sweat-
Haven't run yet. Been on other projects - rebuild a Spec Racer Renault and again back to Thailand to get sailboat ready for ocean crossing again. If you start at about post #11,
http://vettemod.com/forum/showthread.php?t=10667&page=2

you'll see how I assembled the brake set up. Planning on scavenging air from under the belly pan may blow if needed. Will be using temp paint to monitor heat initially. I'm now rethinking the weight and in future may go for smaller cross members.

Cheers Jim

phantomjock said:

Cole Sweat-
Haven't run yet. Been on other projects - rebuild a Spec Racer Renault and again back to Thailand to get sailboat ready for ocean crossing again. If you start at about post #11,
http://vettemod.com/forum/showthread.php?t=10667&page=2

you'll see how I assembled the brake set up. Planning on scavenging air from under the belly pan may blow if needed. Will be using temp paint to monitor heat initially. I'm now rethinking the weight and in future may go for smaller cross members.

Cheers Jim

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Sailboat for ocean crossing?? what size?? I been into sailing for some decades, years ago, before uncle Arthur cut the ability.....

Long ago I read that book by Sir Francis Chichester.....first person to sail around the world ALONE in a ~65' boat......think he did it with one stop in SE Asia region somewhere, and went around both Capes alone, the one around S. America is hair raising, much less his 360 degree roll/capsize....a must read for any guy.....just have to read it, should be mandatory in ALL grade schools world wide.....

73c34me said:

Greetings,

On my 73, I have a welded in 6 point roll bar. The rear 4 legs are welded to the frame on the kick-ups & near the shock mount. I have also boxed in the area where the differential X-member (sombrero) mounts/ bolts to. So with this, I am wondering if the welded X-member behind this is redundant. In the interest of weight loss, it appears that the X-member could be cut-off after the sombrero mounts and capped. Probably not much gained, but it would be zero cost. Thoughts?

Click to expand...

I cut out that crossmember a few years ago. I kept going back and forth as to its contribution to frame strength, but I ran into an issue that made the decision for me. I've got a C4 suspension on my car, and when I changed out the C4 toe rods for C6 toe rods I found out it was a nightmare to get my hands up there to install/remove those parts. After a lot of cussing I just cut the crossmember out. I never really noticed any difference afterward in the feel of the frame stiffness. (IIRC, didn't Chevrolet delete that crossmember in about the '79 model year timeframe?) For full disclosure, I did make a bolt-in crossmember with 1" aluminum square tubing, bolted to the (former) rear swaybar location, but this crossmember is used primarily to hang parts of the exhaust from.

Thanks for all responses. I soon as the dr. Clears me (neck fusion surgery) I will take the cutoff saw to it. Will weigh it too. I made the transmission a removable X and saved a couple of lbs there. Car weight if my notes are correct should be 2970 lb. w/ 1/2 tank fuel. Last check was 3142 lbs @ 1/2 tank.

Looking forward to the weight check!

Sailboat for ocean crossing?? what size?? I been into sailing for some decades, years ago,

Click to expand...

Cheers - Jim