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post #1 of (permalink) Old 12-23-2002, 05:18 PM Thread Starter
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Materials for tranny crossmember/skidplate

I'm getting ready to start building my tranny crossmember/skidplate, but am having some trouble figuring out what materials to use. I want to build a crossmember with removable plates so I don't have to support the tranny every time I want to check something or service it. AFW makes one from tubing, but tubing is a little hard to work with without a bender and some other tools. I was thinking maybe some 1x2 or 1x3, but the problem is that only comes in 1/8" wall. Do you think this would be strong enough? Anything larger and I'm starting to sacrifice ground clearance. Thanks a bunch!
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post #2 of (permalink) Old 12-23-2002, 05:38 PM
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Re: Materials for tranny crossmember/skidplate

I used a piece of 1"x2" steel bar.
It crosses from on side of the frame to the other supporting only the Transmission at the Tranny mount.
This bar is plently strong. I have had the entire weight of my Jeep resting, slamming on rocks without any bending or other problems.
As far as skid plates go I don't have them, My T-18 is 1/2" thick and those DANA 300 T-cases are strong too. So I figured I'll go with as much clearance as possible.
From the side of my Jeep it looks like nothing is under it.

I'd post a picture but my Camera is on the fritz!
post #3 of (permalink) Old 12-24-2002, 10:03 AM
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Re: Materials for tranny crossmember/skidplate

Whether 1 X 2 X 1/8" tubing is strong enough depends on the design and how hard you bash it. It would certainly be strong enough if you design and build it well. Do you have a sketch of what you have in mind?
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post #4 of (permalink) Old 12-24-2002, 04:02 PM
 
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Re: Materials for tranny crossmember/skidplate

I used 1 1/2" x 3" x 1/8" box steel tube and I haven`t had any problems. Plenty stout. Had a nice skid plate bent out of a scrap piece of 1/2" Aluminum, But lost it playing up in the Mt. Hood Nat. Forest. Got another piece though and plan to find a better way to attach it.
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post #5 of (permalink) Old 12-24-2002, 11:37 PM Thread Starter
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Re: Materials for tranny crossmember/skidplate

Jim_Lou - I don't have any sketches, but maybe I'll do some Photoshop work or something. I'm thinking something similar to AFW's skidplate, but instead of using round tubing, us box. Round will just be a PITA. Do you have any suggestions? I'm planning on using angle iron or something on the frame, then I'm going to weld the tubing to that. The tubing will be cut and reweld to make up for the difference in hieghts of the frame and tranny. I just don't know the best way to go aobut making this.

4x401CJ5 - So how exactly did you go about constructing yours? Any pictures?
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post #6 of (permalink) Old 12-25-2002, 11:35 AM
 
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Re: Materials for tranny crossmember/skidplate

I already have the materials and a sketch..don't know how to post it though..

1...the angle iron will be drilled and bolt to the frame ..eliminating the possibility of breaking those nuts loose inside the frame, everytime I need to take it down...
2... the angle iron ears will be welded to the part that bolts to the frame ,with holes to accomodate the mounting bolt.
3...the mounting bolt will pass through the round steel tubing that will be welded into the holes that go through the 1 x 2 square steel tubing that will form the removable part of the skeleton.that the skidplate will be bolted to

I could do a more detailed sketch with a pencil and paper than a mouse.Someone had a simular design posted here on this board at one time and I thought it was a good design except he had urethane bushings in the part that bolted to the angle iron.
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post #7 of (permalink) Old 12-26-2002, 09:10 AM
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Re: Materials for tranny crossmember/skidplate

Well, I'm a little worried about your plan to notch, bend and weld the tube. There is a lot of stress on those welds. They must be done just right or they will crack and come apart after being used for a while. If there's any possibility of a failed weld causing an accident, you should have the entire assembly heat treated when you're finished welding it.

RRich and I gat in a discussion about welding thick material with a 110 Volt wire feeder. I welded two pieces of 5/8" cold rolled, and then put it in the press until it came apart. The significant finding was that the weld didn't break, but along side of the weld was a brittle band of steel. After the plate bent about 30 degrees or so, it broke apart there. The problem was that the thick steel sucked the heat out of the weld bead so quickly that the steel crystalized improperly. Had the piece been heat treated after welding, the joint would have been successful. On thinner material, like 1/8" tube, it's not nearly as likely to occur, but I have to admit that I pay closer attention to preheating and post heating since that little experiment.

As for Unhumen's description, I'm not sure if I follow the plan to attach it to the frame, but it sounds like there is at least one joint there that could be eliminated, and fewer is always better. A couple of months ago I put up a post about how I took care of the nuts where the skidplate bolts to the frame. I think that it's a better solution than bolting a piece of angle there and bolting the skidplate frame to the angle, if that's the plan.

It sure would be nice if you could get a sketch posted.

And as for my skidplate, it's the stock item with some minor modifications - nothing fancy. But then I no longer have to worry about twisting a nut out every time I need to drop it, so I think it will serve.
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post #8 of (permalink) Old 12-26-2002, 10:02 AM
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Re: Materials for tranny crossmember/skidplate

</font><blockquote><font class="small">In reply to:</font><hr />
As far as skid plates go I don't have them, My T-18 is 1/2" thick and those DANA 300 T-cases are strong too. So I figured I'll go with as much clearance as possible.

[/ QUOTE ]

That's totally crazy. You will be buying a new trans and/or t-case soon if you do any wheeling at all.
As far as the topic of the post, go as thick as you can where it counts. For instance, Jaffer built himself a skidplate this fall, didn't go thick enough and it sags a little, he was planning on reinforcing it last I knew (yes, an NV4500 is HEAVY!).
post #9 of (permalink) Old 12-26-2002, 01:57 PM
 
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Re: Materials for tranny crossmember/skidplate

Jammy what about lifting up the motor an inch? You'll have more ground clearance under your jeep. I made my motor mount spacers out of 1x2 bar, i'm not sure how yj mounts differ for tj mounts but i cut off the stud that was sticking out of the mount, drilled ane hole to replace the stud (i think the stud was 5/16 so i drilled a 5/16 hole all the way though and then a 1/2" hole about 1/2 way though the block, rounded the head off with a grinder and pounded it down into the hole) and drilled another hole for the other motor mount bolt and then welded the metal base and metal protective casing to the block. Be sure to wrap the ruber mount with a wet towel so it doesn't break out in flames.

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post #10 of (permalink) Old 12-31-2002, 06:49 PM Thread Starter
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Re: Materials for tranny crossmember/skidplate

Sorry it took me a little bit to respond to this. Anyway, a buddy of mine did up a few sketches. Check them out and let me know what you think.

I searched for the post you referred to about redoing the way it's mounted to the frame. I think I found it, but not sure. It was about welding a new nut into the frame. I'm not sure how that is any different than my stock setup on my YJ.

Another option someone gave me was getting some 1x3x3/16" c-channel and using that for the x-member. I could put a plate on top to box it if I felt the need. What do you think?

BTW - I'll be using a 220v Lincoln for the welding, so do you think I'll still have the problems you talked about as far it becoming brittle around the welds? Thanks a bunch!

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