Fabbing engine/trans cross members

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Fabbing engine/trans cross members

Post  56f100guy on March 3rd 2017, 3:17 am

Im putting a '69 460 in my '56 F-100. I got some 1 1/2"x2 1/2" tube to make an engine cross member. It has to be about 34" wide and I'm figuring about 30 degree angles.

For 'bending' rectangular tube, whats the strongest? Im thinking the kerf (pie cut) and bend would be better than 5 pieces mitered and essentially butt welded.

Im also up in the air on solid engine/trans mounts vs poly. Things will be tight, clearance wise, so I'm thinking rubber is out of the equasion. Some say they can't tell the difference between the two, but I'm thinking poly would be a better choice. Like me, the truck is old, it will likely rattle enough on its own.

Im using 'kerfed' cardboard for templates.... but guess i can't add pics yet?

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Re: Fabbing engine/trans cross members

Post  DILLIGASDAVE on March 3rd 2017, 5:47 am

IMO if it's a thin factory OEM auto trans case then the trans tailshaft always gets a rubber mount regardless of how the engine is mounted, especially if it's a street driven ride. If it's a thicker SFI trans case then either a rubber or urethane mount.

In the past I have done the both the kerf/pie cut & the full miter cut on box/rectangle tubing, either method will work. What's more important than how you made the cut is how you're prepping the joint/seam before welding. If you're using fairly thick tubing you need to grind/chamfer/45* the edges of the metal/weld joint to help aid heat penetration, especially if it's being Mig welded.


Pics need to be hosted elsewhere (like on photobucket) before they can be linked here.
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Re: Fabbing engine/trans cross members

Post  56f100guy on March 3rd 2017, 6:52 am



Thanks for the Photobucket tip. Looks like it works.

As you can maybe tell, I have way too much time on my hands. I spend more time prefabbing than..fabbing.

Ive seen arguments all over the web on rubber with rubber, poly with poly, etc. I think i would tend to agree with that theory. This will be more of a weekend cruiser, but i am banking on being sideways on occasion.

I am using the stock -Lincoln- C6 trans , which has a longer tailshaft and the 'odd' mount. The mounts are half..missing, so I'm just going to build off of whats left and make it more conventional. Looks like I'll need at least a 3" drop but engine is not perfectly placed yet. Pinion angles, etc.

As far as welding, my MIG is a bit small (110v), so i think I'll be dusting off the other Lincoln.. stick welder. Thankfully i have plenty of things to grind ugly welds. I may just tack it up and use a friends 220 MIG welder.

I think the kerf style may be cleaner looking but not as easy. More cutting, less welding.

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Re: Fabbing engine/trans cross members

Post  zbob on March 3rd 2017, 9:49 am

use the Lincoln welder with 7018 rod, turn it up till it frys like bacon, hold the rod a a 45 degree angle and push the rod into the puddle. you will not have to grind nothing then. try it on a left over piece of the same material till you get the frying noise. zbob

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Re: Fabbing engine/trans cross members

Post  Gregaust on March 4th 2017, 3:18 am

The trans must always have a flexible mount , Even when motor plates are used a rubber trans mount stays , or there is risk of breaking the case Sad

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Re: Fabbing engine/trans cross members

Post  56f100guy on March 4th 2017, 3:37 am

Gregaust wrote:The trans must always have a flexible mount , Even when motor plates are used a rubber trans mount stays , or there is risk of breaking the case Sad

Thanks for the info! I have been curious on what the 'engine plate' people use on transmissions.

I think i will be ordering some generic Energy Suspension bushings. The 2.2120 should work. May as well get two sets and make a trans mount of sorts as well.

I was going to start making my x members today but found out very quickly my carbide blade wont cut steel. I knew it wouldn't,  but i tried anyway. Nope.

I'll probably end up making them the 'easy' way.

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Re: Fabbing engine/trans cross members

Post  jeffgfg on March 4th 2017, 10:27 am

I understand the urge to fab the mounts yourself but you can buy bolt in engine and trans mounts both for under 200.00.....no guess work....easy peasy....Good luck!!!

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